Locating and Modeling Regional Earthquakes with Broadband Waveform Data
NASA Astrophysics Data System (ADS)
Tan, Y.; Zhu, L.; Helmberger, D.
2003-12-01
Retrieving source parameters of small earthquakes (Mw < 4.5), including mechanism, depth, location and origin time, relies on local and regional seismic data. Although source characterization for such small events achieves a satisfactory stage in some places with a dense seismic network, such as TriNet, Southern California, a worthy revisit to the historical events in these places or an effective, real-time investigation of small events in many other places, where normally only a few local waveforms plus some short-period recordings are available, is still a problem. To address this issue, we introduce a new type of approach that estimates location, depth, origin time and fault parameters based on 3-component waveform matching in terms of separated Pnl, Rayleigh and Love waves. We show that most local waveforms can be well modeled by a regionalized 1-D model plus different timing corrections for Pnl, Rayleigh and Love waves at relatively long periods, i.e., 4-100 sec for Pnl, and 8-100 sec for surface waves, except for few anomalous paths involving greater structural complexity, meanwhile, these timing corrections reveal similar azimuthal patterns for well-located cluster events, despite their different focal mechanisms. Thus, we can calibrate the paths separately for Pnl, Rayleigh and Love waves with the timing corrections from well-determined events widely recorded by a dense modern seismic network or a temporary PASSCAL experiment. In return, we can locate events and extract their fault parameters by waveform matching for available waveform data, which could be as less as from two stations, assuming timing corrections from the calibration. The accuracy of the obtained source parameters is subject to the error carried by the events used for the calibration. The detailed method requires a Green_s function library constructed from a regionalized 1-D model together with necessary calibration information, and adopts a grid search strategy for both hypercenter and
Bredbeck, T; Rodgers, A; Walter, W
1999-07-23
The velocity structures and source parameters estimated by waveform modeling provide valuable information for CTBT monitoring. The inferred crustal and uppermost mantle structures advance understanding of tectonics and guides regionalization for event location and identification efforts. Estimation of source parameters such as seismic moment, depth and mechanism (whether earthquake, explosion or collapse) is crucial to event identification. In this paper we briefly outline some of the waveform modeling research for CTBT monitoring performed in the last year. In the future we will estimate structure for new regions by modeling waveforms of large well-observed events along additional paths. Of particular interest will be the estimation of velocity structure in aseismic regions such as most of Africa and the Former Soviet Union. Our previous work on aseismic regions in the Middle East, north Africa and south Asia give us confidence to proceed with our current methods. Using the inferred velocity models we plan to estimate source parameters for smaller events. It is especially important to obtain seismic moments of earthquakes for use in applying the Magnitude-Distance Amplitude Correction (MDAC; Taylor et al., 1999) to regional body-wave amplitudes for discrimination and calibrating the coda-based magnitude scales.
Pacific slab beneath northeast China revealed by regional and teleseismic waveform modeling
NASA Astrophysics Data System (ADS)
WANG, X.; Chen, Q. F.; Wei, S.
2015-12-01
Accurate velocity and geometry of the slab is essential for better understanding of the thermal, chemical structure of the mantle earth, as well as geodynamics. Recent tomography studies show similar morphology of the subducting Pacific slab beneath northeast China, which was stagnant in the mantle transition zone with thickness of more than 200km and an average velocity perturbation of ~1.5% [Fukao and Obayashi, 2013]. Meanwhile, waveform-modeling studies reveal that the Pacific slab beneath Japan and Kuril Island has velocity perturbation up to 5% and thickness up to 90km [Chen et al., 2007; Zhan et al., 2014]. These discrepancies are probably caused by the smoothing and limited data coverage in the tomographic inversions. Here we adopted 1D and 2D waveform modeling methods to study the fine structure of Pacific slab beneath northeast China using dense regional permanent and temporary broadband seismic records. The residual S- and P-wave travel time, difference between data and 1D synthetics, shows significant difference between the eastern and western stations. S-wave travel time residuals indicate 5-10s earlier arrivals for stations whose ray path lies within the slab, compared with those out of the slab. Teleseimic waveforms were used to rule out the major contribution of the possible low velocity structure above 200km. Furthermore, we use 2D finite-difference waveform modeling to confirm the velocity perturbation and geometry of the slab. Our result shows that the velocity perturbation in the slab is significantly higher than those reported in travel-time tomography studies. ReferencesChen, M., J. Tromp, D. Helmberger, and H. Kanamori (2007), Waveform modeling of the slab beneath Japan, J. Geophys. Res.-Solid Earth, 112(B2), 19, doi:10.1029/2006jb004394.Fukao, Y., and M. Obayashi (2013), Subducted slabs stagnant above, penetrating through, and trapped below the 660 km discontinuity, J. Geophys. Res.-Solid Earth, 118(11), 5920-5938, doi:10.1002/2013jb010466
Rupture model of the 2011 Mineral, Virginia, earthquake from teleseismic and regional waveforms
Hartzell, Stephen; Mendoza, Carlos; Zeng, Yuehua
2013-01-01
We independently invert teleseismic P waveforms and regional crustal phases to examine the finite fault slip model for the 2011 Mw 5.8 Mineral, Virginia, earthquake. Theoretical and empirical Green's functions are used for the teleseismic and regional models, respectively. Both solutions show two distinct sources each about 2 km across and separated by 2.5 km. The source at the hypocenter is more localized in the regional model leading to a higher peak slip of 130 cm and higher average stress drop of 250 bars compared with 86 cm and 150 bars for the same source in the teleseismic model. Both sources are centered at approximately 8 km depth in the regional model, largely below the aftershock distribution. In the teleseismic model, the sources extend updip to approximately 6 km depth, into the depth range of the aftershocks. The rupture velocity is not well resolved but appears to be near 2.7 km/s.
NASA Astrophysics Data System (ADS)
Swenson, Jennifer Lyn
We use broadband regional waveform modeling of earthquakes in the central Andes to determine seismic properties of the Altiplano crust. Properties of the shear-coupled P-wavetrain (SPL ) from intermediate-depth events provide particularly important information about the structure of the crust. We utilize broadband seismic data recorded at the BANJO and SEDA stations, and synthetic seismograms computed with a reflectivity technique to study the sensitivity of SPL to crustal and upper mantle parameters at regional distances. We find that the long-period SPL-wavetrain is most sensitive to crustal and mantle Poisson's ratios, average crustal velocity, and crustal thickness. A comprehensive grid search method developed to investigate these four parameters suggests that although trade-offs exist between model parameters, models of the Altiplano which provide the best fit between the data and synthetic seismograms are characterized by low Poisson's ratios, low average crustal velocity and thick crust. We apply our grid search technique and sensitivity analysis results to model the full waveforms from 6 intermediate-depth and 2 shallow-focus earthquakes recorded at regional distances by BANJO and SEDA stations. Results suggest that the Altiplano crust is much thicker (55--65 km) and slower (5.75--6.25 km/s) than global average values. Low crustal and mantle Poisson's ratios together with the lack of evidence for a high-velocity lower crust suggests a bulk felsic crustal composition, resulting in an overall weak crust. Our results favor a model of crustal thickening involving large-scale tectonic shortening of a predominantly felsic crust. To better understand the mechanics of earthquake rupture along the South American subduction zone, we have analyzed broadband teleseismic P-waves and utilize single- and multi-station inversion techniques to constrain source characteristics for the 12 November 1996 Peru subduction zone earthquake. Aftershock locations, intensity reports
NASA Astrophysics Data System (ADS)
Ökeler, Ahmet; Gu, Yu Jeffrey; Lerner-Lam, Arthur; Steckler, Michael S.
2009-09-01
We investigate the crust and upper-mantle structures beneath the southern Apennine mountain chain using three-component seismograms from the Calabria-Apennine-Tyrrhenian/Subduction-Collision-Accretion Network (CAT/SCAN) array. Surface wave waveforms from three moderate-sized (Mw > 5.0) regional earthquakes are modelled using multiple frequencies (0.03-0.06 and 0.05-0.2 Hz) and both forward and linearized-inversion algorithms. Our best-fitting shear velocity models clearly reflect the major tectonic units where, for example, the average seismic structure at depths above 50 km beneath Apulia is substantially faster than beneath the Apennine mountain chain. We identify a prominent low-velocity channel under the mountain belt at depths below ~25-30 km and a secondary low-velocity zone at 6-12 km depth near Mt Vulture (a once active volcano). Speed variations between Love and Rayleigh waves provide further constraints on the fabric and dynamic processes. Our analysis indicates that the crustal low-velocity zones are highly anisotropic (maximum 14 per cent) and allow transversely polarized shear waves to travel faster than vertically polarized shear waves. The upper crustal anomaly reveals a layer of highly deformed rocks caused by past collisions and by the active normal faults cutting across the thrust sheets, whereas hot mantle upwelling may be responsible for a high-temperature, partially molten lower crust beneath the southern Apennines.
NASA Astrophysics Data System (ADS)
Saikia, C. K.; Woods, B. B.; Thio, H. K.
-wave path to the surface and becomes critical, developing a head wave by S to P conversion is also indicative of depth. The detailed characteristic of this phase is controlled by the crustal waveguide. The key to calibrating regionalized crustal velocity structure is to determine depths for a set of master events by applying the above methods and then by modeling characteristic features that are recorded on the regional waveforms. The regionalization scheme can also incorporate mixed-path crustal waveguide models for cases in which seismic waves traverse two or more distinctly different crustal structures. We also demonstrate that once depths are established, we need only two-stations travel-time data to obtain reliable epicentral locations using a new adaptive grid-search technique which yields locations similar to those determined using travel-time data from local seismic networks with better azimuthal coverage.
Waveform Tomography of the North Atlantic Region
NASA Astrophysics Data System (ADS)
Celli, Nicolas Luca; Lebedev, Sergei; Schaeffer, Andrew; Gaina, Carmen
2016-04-01
The enormous volumes of newly available, broadband seismic data and the continuing development of waveform tomography techniques present us with an opportunity to resolve the structure of North Atlantic at a new level of detail. Dynamics of the North Atlantic Ridge and the Iceland Hotspot, evolution of the passive margins on both sides of the ocean, and the nature of the upper-mantle flow beneath the region are some of the important fundamental problems that we can make progress on using new, more detailed and accurate models of seismic structure and anisotropy within the lithosphere and underlying mantle. We assemble a very large waveform dataset including all publicly available data in the region, from both permanent and temporary seismic networks and experiments conducted in Northern and Western Europe, Iceland, Canada, USA, Greenland and Russia. The tomographic model is constrained by vertical-component waveform fits, computed using the Automated Multimode Inversion of surface, S and multiple S waves. Each seismogram fit provides a set of linear equations describing 1D average velocity perturbations with respect to a 3D reference velocity model within an approximate sensitivity region between the source and the receiver. The equations are then combined into a large linear system and jointly inverted for a model of shear- and compressional-wave speeds and azimuthal anisotropy within the lithosphere and underlying mantle. The isotropic-average shear speeds reflect the temperature and composition at depth, offering important new information on both regional- and basin-scale lithospheric structure and evolution. Azimuthal anisotropy provides evidence on the past and present deformation in the lithosphere and asthenosphere beneath the region, which can be interpreted together with other evidence from geological and geophysical data and recent plate kinematic models.
Waveform Tomography of the South Atlantic Region
NASA Astrophysics Data System (ADS)
Celli, N. L.; Lebedev, S.; Schaeffer, A. J.; Gaina, C.
2016-12-01
The rapid growth in broadband seismic data, along with developments in waveform tomography techniques, allow us to greatly improve the data sampling in the southern hemisphere and resolve the upper-mantle structure beneath the South Atlantic region at a new level of detail. We have gathered a very large waveform dataset, including all publicly available data from permanent and temporary networks. Our S-velocity tomographic model is constrained by vertical-component waveform fits, computed using the Automated Multimode Inversion of surface, S and multiple S waves. Each seismogram fit provides a set of linear equations describing 1D average velocity perturbations within approximate sensitivity volumes, with respect to a 3D reference model. All the equations are then combined into a large linear system and inverted jointly for a model of shear- and compressional-wave speeds and azimuthal anisotropy within the lithosphere and underlying mantle. The isotropic-average shear speeds are proxies for temperature and composition at depth, while azimuthal anisotropy provides evidence on the past and present deformation in the lithosphere and asthenosphere beneath the region. We resolve the complex boundaries of the mantle roots of South America's and Africa's cratons and the deep low-velocity anomalies beneath volcanic areas in South America. Pronounced lithospheric high seismic velocity anomalies beneath the Argentine Basin suggest that its anomalously deep seafloor, previously attributed to dynamic topography, is mainly due to anomalously cold, thick lithosphere. Major hotspots show low-velocity anomalies extending substantially deeper than those beneath the mid-ocean ridge. The Vema Hotspot shows a major, hot asthenospheric anomaly beneath thick, cold oceanic lithosphere. The mantle lithosphere beneath the Walvis Ridge—a hotspot track—shows normal cooling. The volcanic Cameroon Line, in contrast, is characterized by thin lithosphere beneath the locations of recent
Seismic Waveform Tomography of the Iranian Region
NASA Astrophysics Data System (ADS)
Maggi, A.; Priestley, K.; Jackson, J.
2001-05-01
Surprisingly little is known about the detailed velocity structure of Iran, despite the region's importance in the tectonics of the Middle East. Previous studies have concentrated mainly on fundamental mode surface wave dispersion measurements along isolated paths (e.g.~Asudeh, 1982; Cong & Mitchell, 1998; Ritzwoller et.~al, 1998), and the propagation characteristics of crust and upper mantle body waves (e.g. Hearn & Ni 1994; Rodgers et.~al 1997). We use the partitioned waveform inversion method of Nolet (1990) on several hundred regional waveforms crossing the Iranian region to produce a 3-D seismic velocity map for the crust and upper mantle of the area. The method consists of using long period seismograms from earthquakes with well determined focal mechanisms and depths to constrain 1-D path-averaged shear wave models along regional paths. The constraints imposed on the 1-D models by the seismograms are then combined with independent constraints from other methods (e.g.~Moho depths from reciever function analysis etc.), to solve for the 3-D seismic velocity structure of the region. A dense coverage of fundamental mode rayleigh waves at a period of 100~s ensures good resolution of lithospheric scale structure. We also use 20~s period fundamental mode rayleigh waves and some Pnl wavetrains to make estimates of crustal thickness variations and average crustal velocities. A few deeper events give us some coverage of higher mode rayleigh waves and mantle S waves, which sample to the base of the upper mantle. Our crustal thickness estimates range from 45~km in the southern Zagros mountains, to 40~km in central Iran and 35~km towards the north of the region. We also find inconsistencies between the 1-D models required to fit the vertical and the tranverse seismograms, indicating the presence of anisotropy.
Assessing Accuracy of Waveform Models against Numerical Relativity Waveforms
NASA Astrophysics Data System (ADS)
Pürrer, Michael; LVC Collaboration
2016-03-01
We compare currently available phenomenological and effective-one-body inspiral-merger-ringdown models for gravitational waves (GW) emitted from coalescing black hole binaries against a set of numerical relativity waveforms from the SXS collaboration. Simplifications are used in the construction of some waveform models, such as restriction to spins aligned with the orbital angular momentum, no inclusion of higher harmonics in the GW radiation, no modeling of eccentricity and the use of effective parameters to describe spin precession. In contrast, NR waveforms provide us with a high fidelity representation of the ``true'' waveform modulo small numerical errors. To focus on systematics we inject NR waveforms into zero noise for early advanced LIGO detector sensitivity at a moderately optimistic signal-to-noise ratio. We discuss where in the parameter space the above modeling assumptions lead to noticeable biases in recovered parameters.
Regional waveform calibration in the Pamir-Hindu Kush region
NASA Astrophysics Data System (ADS)
Zhu, Lupei; Helmberger, Donald V.; Saikia, Chandan K.; Woods, Bradley B.
1997-10-01
Twelve moderate-magnitude earthquakes (mb 4-5.5) in the Pamir-Hindu Kush region are investigated to determine their focal mechanisms and to relocate them using their regional waveform records at two broadband arrays, the Kyrgyzstan Regional Network (KNET), and the 1992 Pakistan Himalayas seismic experiment array (PAKH) in northern Pakistan. We use the "cut-and-paste" source estimation technique to invert the whole broadband waveforms for mechanisms and depths, assuming a one-dimensional velocity model developed for the adjacent Tibetan plateau. For several large events the source mechanisms obtained agree with those available from the Harvard centroid moment tensor (CMT) solutions. An advantage of using regional broadband waveforms is that focal depths can be better constrained either from amplitude ratios of Pnl to surface waves for crustal events or from time separation between the direct P and the shear-coupled P wave (sPn + sPmP) for mantle events. All the crustal events are relocated at shallower depths compared with their International Seismological Centre bulletin or Harvard CMT depths. After the focal depths are established, the events are then relocated horizontally using their first-arrival times. Only minor offsets in epicentral location are found for all mantle events and the bigger crustal events, while rather large offsets (up to 30 km) occur for the smaller crustal events. We also tested the performance of waveform inversion using only two broadband stations, one from the KNET array in the north of the region and one from the PAKH array in the south. We found that this geometry is adequate for determining focal depths and mechanisms of moderate size earthquakes in the Pamir-Hindu Kush region.
App, F.N.; Jones, E.M.; Bos, R.J.
1997-11-01
The identification of an underground nuclear test from its seismic signal recorded by seismometers at regional distances is one of the fundamental scientific goals of the Comprehensive Test Ban Treaty R and D Program. The work being reported here addresses the issue of event discrimination through the use of computer models that use realistic simulations of nuclear explosions in various settings for the generation of near-regional and regional synthetic seismograms. The study exercises some unique, recently developed computer modeling capabilities that heretofore have not been available for discrimination studies. A variety of source conditions and regional paths are investigated. Under the assumptions of the study, conclusions are: (1) spall, non-linear deformation, and depth-of-burial do not substantially influence the near-regional signal and (2) effects due to basins along the regional path very much dominate over source region geology in influencing the signal at regional distances. These conclusions, however, are relevant only for the frequencies addressed, which span the range from 0.1 to 1 Hz for the regional calculations and 0.1 to 3 Hz for the near-regional calculations. They also are relevant only for the crudely ``China-like`` basin, crust, and mantle properties used in the study. If it is determined that further investigations are required, researchers may use this study as a template for such work.
NASA Astrophysics Data System (ADS)
Swenson, Jennifer L.; Beck, Susan L.; Zandt, George
2000-01-01
We have modeled the full waveforms from six intermediate-depth and two shallow earthquakes recorded at regional distances by the BANJO Broadband Andean Joint Experiment (BANJO) and Seismic Exploration of the Deep Altiplano (SEDA) portable seismic networks in the central Andes. In this study we utilize data from those BANJO and SEDA stations located within the Altiplano and Eastern Cordillera. We used reflectivity synthetic seismograms and a grid search to constrain four parameters of the Altiplano-Eastern Cordillera lithosphere: crustal thickness, average crustal velocity (Vp), and crustal and upper mantle Poisson's ratios (σcrust and σmantle). Using our grid search, we investigated the crustal and upper mantle structure along 36 individual event station paths and applied forward modeling to 56 event station paths. Robust models for the Altiplano that provide the best overall fit between the data and synthetic seismograms are characterized by an average Vp of 5.75-6.25 km/s, crustal thicknesses of 60-65 km, σcrust = 0.25, and σmantle = 0.27-0.29. We find a north-south variation in the structure of the Altiplano, with the crust south of the BANJO transect characterized by either lower than average crustal P wave velocities or a slightly higher σcrust relative to crust north of the BANJO transect. These results are consistent with a model of crustal thickening caused predominantly by tectonic shortening of felsic crust, rather than by underplating or magmatic intrusion from the mantle.
NASA Astrophysics Data System (ADS)
Maggi, A.; Tromp, J.; Debayle, E.; Barruol, G.
2005-12-01
We present an anisotropic Sv-wave speed tomographic model for the Pacific Ocean region derived from multi-mode waveform inversion of more than 56,000 vertical component seismograms. Most of the data are from the Global Seismic Network, but we include important data from ten broadband seismographs deployed in French Polynesia as part of the Polynesian Lithosphere and Upper Mantle Experiment. This extra data has improved lateral resolution in the south Pacific region, leading to the identification of localized, vertically trending low velocity anomalies associated with the Society and Macdonald hot-spots. An age-dependent average cross-section of our tomographic model shows the lithosphere thickening and cooling with increasing age as predicted by a purely diffusive cooling mechanism. The tomography was performed assuming 2D frequency-independent Gaussian-shaped sensitivity kernels around the surface wave ray-paths, and ray-theoretical depth dependence of the surface wave sensitivity. We validate the 3D tomographic model by calculating full 3D synthetic seismograms using the spectral element method. We estimate the quality of our tomographic inversion by making multi-taper phase and amplitude measurements of the differences between observed seismograms and 3D synthetics. Preliminary inversion of such measurements made on fundamental mode surface waves indicates that the residual discrepancies between our 3D tomographic model and the real Earth structure are localized in regions of strong upper mantle heterogeneity (e.g. subduction zones), for which the ray-theoretical approximations made during the tomographic inversion are most likely to break down.
Finite-fault slip model of the 2011 Mw 5.6 Prague, Oklahoma earthquake from regional waveforms
Sun, Xiaodan; Hartzell, Stephen
2014-01-01
The slip model for the 2011 Mw 5.6 Prague, Oklahoma, earthquake is inferred using a linear least squares methodology. Waveforms of six aftershocks recorded at 21 regional stations are used as empirical Green's functions (EGFs). The solution indicates two large slip patches: one located around the hypocenter with a depth range of 3–5.5 km; the other located to the southwest of the epicenter with a depth range from 7.5 to 9.5 km. The total moment of the solution is estimated at 3.37 × 1024 dyne cm (Mw 5.65). The peak slip and average stress drop for the source at the hypocenter are 70 cm and 90 bars, respectively, approximately one half the values for the Mw 5.8 2011 Mineral, Virginia, earthquake. The stress drop averaged over all areas of slip is 16 bars. The relatively low peak slip and stress drop may indicate an induced component in the origin of the Prague earthquake from deep fluid injection.
Finite-fault slip model of the 2011 Mw 5.6 Prague, Oklahoma earthquake from regional waveforms
NASA Astrophysics Data System (ADS)
Sun, Xiaodan; Hartzell, Stephen
2014-06-01
The slip model for the 2011 Mw 5.6 Prague, Oklahoma, earthquake is inferred using a linear least squares methodology. Waveforms of six aftershocks recorded at 21 regional stations are used as empirical Green's functions (EGFs). The solution indicates two large slip patches: one located around the hypocenter with a depth range of 3-5.5 km; the other located to the southwest of the epicenter with a depth range from 7.5 to 9.5 km. The total moment of the solution is estimated at 3.37 × 1024 dyne cm (Mw 5.65). The peak slip and average stress drop for the source at the hypocenter are 70 cm and 90 bars, respectively, approximately one half the values for the Mw 5.8 2011 Mineral, Virginia, earthquake. The stress drop averaged over all areas of slip is 16 bars. The relatively low peak slip and stress drop may indicate an induced component in the origin of the Prague earthquake from deep fluid injection.
A model for tailored-waveform radiofrequency sheaths
NASA Astrophysics Data System (ADS)
Chabert, P.; Turner, M. M.
2017-06-01
The sheath physics of radiofrequency plasmas excited by a sinusoidal waveform is reasonably well understood, but the existing models are complicated and are not easily extended to the more complex waveforms recently introduced in applications. Turner and Chabert (2014 Appl. Phys. Lett. 104 164102) proposed a model for collisionless sheaths that can easily be solved for arbitrary waveforms. In this paper we extend this model to the case of collisional sheaths in the intermediate pressure regime. Analytical expressions are derived for the electric field, the electric potential and the density profiles in the sheath region. The collisionless and collisional models are compared for a pulsed-voltage waveform.
Seismic waveform modeling over cloud
NASA Astrophysics Data System (ADS)
Luo, Cong; Friederich, Wolfgang
2016-04-01
With the fast growing computational technologies, numerical simulation of seismic wave propagation achieved huge successes. Obtaining the synthetic waveforms through numerical simulation receives an increasing amount of attention from seismologists. However, computational seismology is a data-intensive research field, and the numerical packages usually come with a steep learning curve. Users are expected to master considerable amount of computer knowledge and data processing skills. Training users to use the numerical packages, correctly access and utilize the computational resources is a troubled task. In addition to that, accessing to HPC is also a common difficulty for many users. To solve these problems, a cloud based solution dedicated on shallow seismic waveform modeling has been developed with the state-of-the-art web technologies. It is a web platform integrating both software and hardware with multilayer architecture: a well designed SQL database serves as the data layer, HPC and dedicated pipeline for it is the business layer. Through this platform, users will no longer need to compile and manipulate various packages on the local machine within local network to perform a simulation. By providing users professional access to the computational code through its interfaces and delivering our computational resources to the users over cloud, users can customize the simulation at expert-level, submit and run the job through it.
NASA Astrophysics Data System (ADS)
Nuber, André; Manukyan, Edgar; Maurer, Hansruedi
2014-05-01
Conventional methods of interpreting seismic data rely on filtering and processing limited portions of the recorded wavefield. Typically, either reflections, refractions or surface waves are considered in isolation. Particularly in near-surface engineering and environmental investigations (depths less than, say 100 m), these wave types often overlap in time and are difficult to separate. Full waveform inversion is a technique that seeks to exploit and interpret the full information content of the seismic records without the need for separating events first; it yields models of the subsurface at sub-wavelength resolution. We use a finite element modelling code to solve the 2D elastic isotropic wave equation in the frequency domain. This code is part of a Gauss-Newton inversion scheme which we employ to invert for the P- and S-wave velocities as well as for density in the subsurface. For shallow surface data the use of an elastic forward solver is essential because surface waves often dominate the seismograms. This leads to high sensitivities (partial derivatives contained in the Jacobian matrix of the Gauss-Newton inversion scheme) and thus large model updates close to the surface. Reflections from deeper structures may also include useful information, but the large sensitivities of the surface waves often preclude this information from being fully exploited. We have developed two methods that balance the sensitivity distributions and thus may help resolve the deeper structures. The first method includes equilibrating the columns of the Jacobian matrix prior to every inversion step by multiplying them with individual scaling factors. This is expected to also balance the model updates throughout the entire subsurface model. It can be shown that this procedure is mathematically equivalent to balancing the regularization weights of the individual model parameters. A proper choice of the scaling factors required to balance the Jacobian matrix is critical. We decided to
Lamb, Frederick K.; Boutloukos, Stratos; Van Wassenhove, Sandor; Chamberlain, Robert T.; Lo, Ka Ho; Clare, Alexander; Yu Wenfei; Miller, M. Coleman
2009-11-20
We investigate further a model of the accreting millisecond X-ray pulsars we proposed earlier. In this model, the X-ray-emitting regions of these pulsars are near their spin axes but move. This is to be expected if the magnetic poles of these stars are close to their spin axes, so that accreting gas is channeled there. As the accretion rate and the structure of the inner disk vary, gas is channeled along different field lines to different locations on the stellar surface, causing the X-ray-emitting areas to move. We show that this 'nearly aligned moving spot model' can explain many properties of the accreting millisecond X-ray pulsars, including their generally low oscillation amplitudes and nearly sinusoidal waveforms; the variability of their pulse amplitudes, shapes, and phases; the correlations in this variability; and the similarity of the accretion- and nuclear-powered pulse shapes and phases in some. It may also explain why accretion-powered millisecond pulsars are difficult to detect, why some are intermittent, and why all detected so far are transients. This model can be tested by comparing with observations the waveform changes it predicts, including the changes with accretion rate.
Modeling measured glottal volume velocity waveforms.
Verneuil, Andrew; Berry, David A; Kreiman, Jody; Gerratt, Bruce R; Ye, Ming; Berke, Gerald S
2003-02-01
The source-filter theory of speech production describes a glottal energy source (volume velocity waveform) that is filtered by the vocal tract and radiates from the mouth as phonation. The characteristics of the volume velocity waveform, the source that drives phonation, have been estimated, but never directly measured at the glottis. To accomplish this measurement, constant temperature anemometer probes were used in an in vivo canine constant pressure model of phonation. A 3-probe array was positioned supraglottically, and an endoscopic camera was positioned subglottically. Simultaneous recordings of airflow velocity (using anemometry) and glottal area (using stroboscopy) were made in 3 animals. Glottal airflow velocities and areas were combined to produce direct measurements of glottal volume velocity waveforms. The anterior and middle parts of the glottis contributed significantly to the volume velocity waveform, with less contribution from the posterior part of the glottis. The measured volume velocity waveforms were successfully fitted to a well-known laryngeal airflow model. A noninvasive measured volume velocity waveform holds promise for future clinical use.
NASA Technical Reports Server (NTRS)
Bhattacharyya, Joydeep; Sheehan, Anne F.; Tiampo, Kristy; Rundle, John
1999-01-01
In this study, we analyze regional seismograms to obtain the crustal structure in the eastern Great Basin and western Colorado plateau. Adopting a for- ward-modeling approach, we develop a genetic algorithm (GA) based parameter search technique to constrain the one-dimensional crustal structure in these regions. The data are broadband three-component seismograms recorded at the 1994-95 IRIS PASSCAL Colorado Plateau to Great Basin experiment (CPGB) stations and supplemented by data from U.S. National Seismic Network (USNSN) stations in Utah and Nevada. We use the southwestern Wyoming mine collapse event (M(sub b) = 5.2) that occurred on 3 February 1995 as the seismic source. We model the regional seismograms using a four-layer crustal model with constant layer parameters. Timing of teleseismic receiver functions at CPGB stations are added as an additional constraint in the modeling. GA allows us to efficiently search the model space. A carefully chosen fitness function and a windowing scheme are added to the algorithm to prevent search stagnation. The technique is tested with synthetic data, both with and without random Gaussian noise added to it. Several separate model searches are carried out to estimate the variability of the model parameters. The average Colorado plateau crustal structure is characterized by a 40-km-thick crust with velocity increases at depths of about 10 and 25 km and a fast lower crust while the Great Basin has approximately 35- km-thick crust and a 2.9-km-thick sedimentary layer.
Full-waveform inversion of the Japanese Islands region
NASA Astrophysics Data System (ADS)
SimutÄ--, SaulÄ--; Steptoe, Hamish; Cobden, Laura; Gokhberg, Alexey; Fichtner, Andreas
2016-05-01
We present a full-waveform tomographic model of the crust and upper mantle beneath the Japanese Islands region. This is based on the combination of GPU-accelerated spectral-element wavefield simulations, adjoint techniques, and nonlinear optimization. Our model explains complete seismic waveforms of events not used in the inversion in the period range from 20 to 80 s. Quantitative resolution analysis indicates that resolution lengths within the well-covered areas are around 150 km in the horizontal and around 30 km in the vertical directions. In addition to the high-velocity signatures of known lithospheric slabs in the region, our model reveals a pronounced low-velocity anomaly beneath the volcanic island of Ulleung in the Sea of Japan, reaching -19% around 100 km depth. The Ulleung anomaly originates at or above the Pacific slab, rises vertically upward to the base of the Philippine Sea slab at ˜200 km depth, circumvents it in NW direction, and then significantly strengthens in the uppermost mantle above the Philippine Sea slab. Among the numerous hypotheses for the generation of low-velocity anomalies in subduction systems, those invoking instabilities before or when a slab enters the transition zone seem most likely. The age and fast subduction of the Pacific slab may facilitate the transport of fluids into the transition zone. This may promote the reduction in viscosity and the onset of convective upwelling, aided by ambient mantle flow, such as return flow within the mantle wedge.
NASA Astrophysics Data System (ADS)
Negi, Sanjay S.; Paul, Ajay; Cesca, Simone; Kamal; Kriegerowski, Marius; Mahesh, P.; Gupta, Sandeep
2017-08-01
In order to understand present day earthquake kinematics at the Indian plate boundary, we analyse seismic broadband data recorded between 2007 and 2015 by the regional network in the Garhwal-Kumaun region, northwest Himalaya. We first estimate a local 1-D velocity model for the computation of reliable Green's functions, based on 2837 P-wave and 2680 S-wave arrivals from 251 well located earthquakes. The resulting 1-D crustal structure yields a 4-layer velocity model down to the depths of 20 km. A fifth homogeneous layer extends down to 46 km, constraining the Moho using travel-time distance curve method. We then employ a multistep moment tensor (MT) inversion algorithm to infer seismic moment tensors of 11 moderate earthquakes with Mw magnitude in the range 4.0-5.0. The method provides a fast MT inversion for future monitoring of local seismicity, since Green's functions database has been prepared. To further support the moment tensor solutions, we additionally model P phase beams at seismic arrays at teleseismic distances. The MT inversion result reveals the presence of dominant thrust fault kinematics persisting along the Himalayan belt. Shallow low and high angle thrust faulting is the dominating mechanism in the Garhwal-Kumaun Himalaya. The centroid depths for these moderate earthquakes are shallow between 1 and 12 km. The beam modeling result confirm hypocentral depth estimates between 1 and 7 km. The updated seismicity, constrained source mechanism and depth results indicate typical setting of duplexes above the mid crustal ramp where slip is confirmed along out-of-sequence thrusting. The involvement of Tons thrust sheet in out-of-sequence thrusting indicate Tons thrust to be the principal active thrust at shallow depth in the Himalayan region. Our results thus support the critical taper wedge theory, where we infer the microseismicity cluster as a result of intense activity within the Lesser Himalayan Duplex (LHD) system.
NASA Astrophysics Data System (ADS)
Alvarado, Patricia; Beck, Susan; Zandt, George; Araujo, Mario; Triep, Enrique
2005-11-01
-7 km. Overall, the western part of the entire region is more seismically active than the eastern part. We postulate that this is related to the presence of different pre-Andean geological terranes. We also find evidence for different average crustal models for those terranes. Better-fitting synthetic seismograms result using a higher P-wave velocity, a smaller average S-wave velocity and a thicker crust for seismic ray paths travelling through the crust of the western Sierras Pampeanas (Vp= 6.2-6.4 km s-1, Vp/Vs > 1.80, th = 45-55 km) than those of the eastern Sierras Pampeanas (Vp= 6.0-6.2 km s-1, Vp/Vs < 1.70, th = 27-35 km). In addition, we observed an apparent distribution of reverse crustal earthquakes along the suture that connects those terranes. Finally, we estimated average P and T axes over the CHARGE period. The entire region showed P- and T-axis orientations of 275° and 90°, plunging 6° and 84°, respectively.
NASA Astrophysics Data System (ADS)
Wang, Xin; Wei, Shengji; Bradley, Kyle Edward
2017-04-01
Global earthquake catalogs provide important first-order constraints on the geometries of active faults. However, the precision of location and focal mechanism parameters in modern global catalogs is typically insufficient to resolve the detailed geometry of many important faults. This issue is particularly critical in subduction zone region, where most great earthquakes take place. The current Slab1.0 have smooth fault geometries, and cannot adequately address local structural complexities that are critical for understanding earthquake rupture pattern, coseismic slip distribution, and interseismic coupling and etc. However, more detailed information about fault geometries can be obtained by careful relocation and modeling waveform of earthquake sequences. Here, we refine the geometry of two active faults in the Mentawai region offshore of Sumatra, Indonesia. This region is a seismic gap in the Sumatran subduction zone, where the 2007 Mw8.4 Bengkulu and 2010 Mw7.8 Mentawai earthquake sequences have partially ruptured the frictionally locked megathrust but a great earthquake has not yet to occur. In addition, two smaller earthquakes in 2005 (Mw6.9) and 2009 (Mw6.7) with steeply dipping fault plane solutions have been identified as backthrust events by Singh et al. (2010) based on structural constraints from seismic reflection profiles. Wiseman et al. (2011) provided geodetic evidence to support the statement that these two earthquake sequences occurred on a major backthrust fault underlying the forearc islands. However, the combination of a small number of focal mechanisms in the available catalog and large uncertainties in both earthquake locations and fault plane solutions severely limits our understanding of the geometry of both the megathrust and backthrust faults. We take advantage of the global seismic stations and conduct broadband waveform modeling for medium size earthquakes (M>4.5) to refine their source parameters, which include location, in particular
Radar altimeter waveform modeled parameter recovery. [SEASAT-1 data
NASA Technical Reports Server (NTRS)
1981-01-01
Satellite-borne radar altimeters include waveform sampling gates providing point samples of the transmitted radar pulse after its scattering from the ocean's surface. Averages of the waveform sampler data can be fitted by varying parameters in a model mean return waveform. The theoretical waveform model used is described as well as a general iterative nonlinear least squares procedures used to obtain estimates of parameters characterizing the modeled waveform for SEASAT-1 data. The six waveform parameters recovered by the fitting procedure are: (1) amplitude; (2) time origin, or track point; (3) ocean surface rms roughness; (4) noise baseline; (5) ocean surface skewness; and (6) altitude or off-nadir angle. Additional practical processing considerations are addressed and FORTRAN source listing for subroutines used in the waveform fitting are included. While the description is for the Seasat-1 altimeter waveform data analysis, the work can easily be generalized and extended to other radar altimeter systems.
Seismic Structure of India from Regional Waveform Matching
NASA Astrophysics Data System (ADS)
Gaur, V.; Maggi, A.; Priestley, K.; Rai, S.
2003-12-01
We use a neighborhood adaptive grid search procedure and reflectivity synthetics to model regional distance range (500-2000~km) seismograms recorded in India and to determine the variation in the crust and uppermost mantle structure across the subcontinent. The portions of the regional waveform which are most influenced by the crust and uppermost mantle structure are the 10-100~s period Pnl and fundamental mode surface waves. We use the adaptive grid search algorithm to match both portions of the seismogram simultaneously. This procedure results in a family of 1-D path average crust and upper mantle velocity and attenuation models whose propagation characteristics closely match those of the real Earth. Our data set currently consist of ˜20 seismograms whose propagation paths are primarily confined to the Ganges Basin in north India and the East Dharwar Craton of south India. The East Dharwar Craton has a simple and uniform structure consisting of a 36+/-2 km thick two layer crust, and an uppermost mantle with a sub-Moho velocity of 4.5~km/s. The structure of northern India is more complicated, with pronounced low velocities in the upper crustal layer due to the large sediment thicknesses in the Ganges basin.
Velocity Structure Determination Through Seismic Waveform Modeling and Time Deviations
NASA Astrophysics Data System (ADS)
Savage, B.; Zhu, L.; Tan, Y.; Helmberger, D. V.
2001-12-01
Through the use of seismic waveforms recorded by TriNet, a dataset of earthquake focal mechanisms and deviations (time shifts) relative to a standard model facilitates the investigation of the crust and uppermost mantle of southern California. The CAP method of focal mechanism determination, in use by TriNet on a routine basis, provides time shifts for surface waves and Pnl arrivals independently relative to the reference model. These shifts serve as initial data for calibration of local and regional seismic paths. Time shifts from the CAP method are derived by splitting the Pnl section of the waveform, the first arriving Pn to just before the arrival of the S wave, from the much slower surface waves then cross-correlating the data with synthetic waveforms computed from a standard model. Surface waves interact with the entire crust, but the upper crust causes the greatest effect. Whereas, Pnl arrivals sample the deeper crust, upper mantle, and source region. This natural division separates the upper from lower crust for regional calibration and structural modeling and allows 3-D velocity maps to be created using the resulting time shifts. Further examination of Pnl and other arrivals which interact with the Moho illuminate the complex nature of this boundary. Initial attempts at using the first 10 seconds of the Pnl section to determine upper most mantle structure have proven insightful. Two large earthquakes north of southern California in Nevada and Mammoth Lakes, CA allow the creation of record sections from 200 to 600 km. As the paths swing from east to west across southern California, simple 1-D models turn into complex structure, dramatically changing the waveform character. Using finite difference models to explain the structure, we determine that a low velocity zone is present at the base of the crust and extends to 100 km in depth. Velocity variations of 5 percent of the mantle in combination with steeply sloping edges produces complex waveform variations
Finite-Fault Analysis Using Regional Broadband Waveforms: The 2004 Parkfield, California Earthquake
NASA Astrophysics Data System (ADS)
Mendoza, C.; Hartzell, S.
2007-05-01
Global improvements in seismic-station coverage and data quality have resulted in the increased use of broadband waveforms in finite-fault studies of the earthquake source. These improvements have also prompted the use of regional waveforms in rapid or real-time derivations of the earthquake rupture history. We examine the applicability of regional records to identify the properties of an extended source by conducting a finite-fault analysis of the Mw 6.0 Parkfield, California, earthquake of 28 September 2004. This earthquake was recorded by more than 80 broadband stations at distances less than 5 degrees from the epicenter. We invert three- component displacement waveforms recorded at the 14 stations located within 2 degrees of the epicenter using a general Northern California crustal structure and a bandpass filter with corners of 0.2 and 1.0 Hz. The resulting rupture model shows coseismic slip extending primarily to the northwest with a peak slip of 60 centimeters at a distance of about 15 km from the hypocenter. This model is compared against results obtained using strong motion and geodetic data. We also examine the use of waveforms recorded at more distant sites by comparing them against synthetic waveforms predicted by the inferred slip model and conduct several tests using different stations at differing azimuths to evaluate the effects of station distribution on the finite-fault results. These tests are useful for assessing the limitations of finite-fault inversion schemes in the routine derivation of the earthquake rupture history using real-time regional waveform data.
An adaptive subspace trust-region method for frequency-domain seismic full waveform inversion
NASA Astrophysics Data System (ADS)
Zhang, Huan; Li, Xiaofan; Song, Hanjie; Liu, Shaolin
2015-05-01
Full waveform inversion is currently considered as a promising seismic imaging method to obtain high-resolution and quantitative images of the subsurface. It is a nonlinear ill-posed inverse problem, the main difficulty of which that prevents the full waveform inversion from widespread applying to real data is the sensitivity to incorrect initial models and noisy data. Local optimization theories including Newton's method and gradient method always lead the convergence to local minima, while global optimization algorithms such as simulated annealing are computationally costly. To confront this issue, in this paper we investigate the possibility of applying the trust-region method to the full waveform inversion problem. Different from line search methods, trust-region methods force the new trial step within a certain neighborhood of the current iterate point. Theoretically, the trust-region methods are reliable and robust, and they have very strong convergence properties. The capability of this inversion technique is tested with the synthetic Marmousi velocity model and the SEG/EAGE Salt model. Numerical examples demonstrate that the adaptive subspace trust-region method can provide solutions closer to the global minima compared to the conventional Approximate Hessian approach and the L-BFGS method with a higher convergence rate. In addition, the match between the inverted model and the true model is still excellent even when the initial model deviates far from the true model. Inversion results with noisy data also exhibit the remarkable capability of the adaptive subspace trust-region method for low signal-to-noise data inversions. Promising numerical results suggest this adaptive subspace trust-region method is suitable for full waveform inversion, as it has stronger convergence and higher convergence rate.
2007-09-01
successfully for global and regional mantle tomography at Berkeley since 1995. In the subregion of study, our “N-Born” model is parameterized at...waveforms, Geophys. J. Int. 143: 709–728. Panning, M. and B. Romanowicz (2004). Inferences on flow at the base of Earth’s mantle based on seismic...CALIBRATION OF THREE-DIMENSIONAL UPPER MANTLE STRUCTURE IN EURASIA USING REGIONAL AND TELESEISMIC FULL WAVEFORM SEISMIC DATA Barbara Romanowicz1
Adjoint Tomography of Taiwan Region: From Travel-Time Toward Waveform Inversion
NASA Astrophysics Data System (ADS)
Huang, H. H.; Lee, S. J.; Tromp, J.
2014-12-01
The complicated tectonic environment such as Taiwan region can modulate the seismic waveform severely and hamper the discrimination and the utilization of later phases. Restricted to the use of only first arrivals of P- and S-wave, the travel-time tomographic models of Taiwan can simulate the seismic waveform barely to a frequency of 0.2 Hz to date. While it has been sufficient for long-period studies, e.g. source inversion, this frequency band is still far from the applications to the community and high-resolution studies. To achieve a higher-frequency simulation, more data and the considerations of off-path and finite-frequency effects are necessary. Based on the spectral-element and the adjoint method recently developed, we prepared 94 MW 3.5-6.0 earthquakes with well-defined location and focal mechanism solutions from Real-Time Moment Tensor Monitoring System (RMT), and preformed an iterative gradient-based inversion employing waveform modeling and finite-frequency measurements of adjoint method. By which the 3-D sensitivity kernels are taken into account realistically and the full waveform information are naturally sought, without a need of any phase pick. A preliminary model m003 using 10-50 sec data was demonstrated and compared with previous travel-time models. The primary difference appears in the mountainous area, where the previous travel-time model may underestimate the S-wave speed in the upper crust, but overestimates in the lower crust.
Fast Prediction and Evaluation of Gravitational Waveforms Using Surrogate Models
NASA Astrophysics Data System (ADS)
Field, Scott E.; Galley, Chad R.; Hesthaven, Jan S.; Kaye, Jason; Tiglio, Manuel
2014-07-01
We propose a solution to the problem of quickly and accurately predicting gravitational waveforms within any given physical model. The method is relevant for both real-time applications and more traditional scenarios where the generation of waveforms using standard methods can be prohibitively expensive. Our approach is based on three offline steps resulting in an accurate reduced order model in both parameter and physical dimensions that can be used as a surrogate for the true or fiducial waveform family. First, a set of m parameter values is determined using a greedy algorithm from which a reduced basis representation is constructed. Second, these m parameters induce the selection of m time values for interpolating a waveform time series using an empirical interpolant that is built for the fiducial waveform family. Third, a fit in the parameter dimension is performed for the waveform's value at each of these m times. The cost of predicting L waveform time samples for a generic parameter choice is of order O(mL+mcfit) online operations, where cfit denotes the fitting function operation count and, typically, m ≪L. The result is a compact, computationally efficient, and accurate surrogate model that retains the original physics of the fiducial waveform family while also being fast to evaluate. We generate accurate surrogate models for effective-one-body waveforms of nonspinning binary black hole coalescences with durations as long as 105M, mass ratios from 1 to 10, and for multiple spherical harmonic modes. We find that these surrogates are more than 3 orders of magnitude faster to evaluate as compared to the cost of generating effective-one-body waveforms in standard ways. Surrogate model building for other waveform families and models follows the same steps and has the same low computational online scaling cost. For expensive numerical simulations of binary black hole coalescences, we thus anticipate extremely large speedups in generating new waveforms with a
Full Waveform Seismic Inversion for the Japan Region
NASA Astrophysics Data System (ADS)
Žukauskaitė, Saulė; Steptoe, Hamish; Fichtner, Andreas
2014-05-01
We present a seismic tomography model for the Japan archipelago obtained using full waveform inversion and adjoint methods. A high-resolution seismic velocity model is essential for Japan as means to comprehend and characterize the complexity of the tectonic setting, and to further our understanding of earthquake sources and rupture propagation. The study area covers the Japanese islands - an area between 20°-50°N and 130°-160°E - and extends to a maximum depth of 500 km. In virtue of complicated tectonics and resulting high seismicity, dense seismic networks are present in Japan and surrounding countries. We make use of broadband data from three networks - F-net in Japan, BATS in Taiwan, and notably, the National Earthquake Network in South Korea. Due to access difficulties, data from this network had not been used in the preceding tomographic study of the same area. We use >50 carefully selected earthquakes, located within the model area and occurring between 1999 and the present. Magnitudes of the events are restricted to 5≤Mw≤6.9 for a point source approximation to be valid. A spectral-element method is used for forward waveform calculation, which comes with the geometric flexibility of finite-elements method and the accuracy of spectral methods. To quantify differences between the observed and synthetic waveforms, we use time-frequency misfits, which exploit the evolution of the frequency content of the data in time. The sensitivities (Fréchet kernels) are then calculated using adjoint methods. The employed methodology allows us to explain the data of dominant period as low as 10 s. To prevent possible over-fitting of the data, we ensure that final misfits are not lower than those obtained if additional (not yet used) data are incorporated. The final results of this study will contribute to the 'Comprehensive Earth Model' being developed by the Computational Seismology group at ETH, with the aim to represent the snapshot of the current knowledge of
NASA Astrophysics Data System (ADS)
Garth, Thomas; Rietbrock, Andreas; Hicks, Steve; Fuenzalida Velasco, Amaya; Casarotti, Emanuele; Spinuso, Alessandro
2015-04-01
The VERCE platform is an online portal that allows full waveform simulations to be run for any region where a suitable velocity model exists. We use this facility to simulate the waveforms from aftershock earthquakes from the 2014 Pisagua earthquake, and 2010 Maule earthquake that occurred at the subduction zone mega thrust in Northern and Central Chile respectively. Simulations are performed using focal mechanisms from both global earthquake catalogues, and regional earthquake catalogues. The VERCE platform supports specFEM Cartesian, and simulations are run using meshes produced by CUBIT. The full waveform modelling techniques supported on the VERCE platform are used to test the validity of a number of subduction zone velocity models from the Chilean subduction zone. For the Maule earthquake we use a 2D and 3D travel time tomography model of the rupture area (Hicks et al. 2011; 2014). For the Pisagua earthquake we test a 2D/3D composite velocity model based on tomographic studies of the region (e.g. Husen et al. 2000, Contreyes-Reyes et al. 2012) and slab1.0 (Hayes et al. 2012). Focal mechanisms from the cGMT catalogue and local focal mechanisms calculated using ISOLA (e.g. Agurto et al. 2012) are used in the simulations. The waveforms produced are directly compared to waveforms recorded on the temporary deployment for the Maule earthquake aftershocks, and waveforms recorded on the IPOC network for the Pisagua earthquake aftershocks. This work demonstrates how the VERCE platform allows waveforms from the full 3D simulations to be easily produced, allowing us to quantify the validity of both the velocity model and the source mechanisms. These simulations therefore provide an independent test of the velocity models produced synthetically and by travel time tomography studies. Initial results show that the waveform is reasonably well reproduced in the 0.05 - 0.25 frequency band using a refined 3D travel time tomography, and locally calculated focal mechanisms.
Solving seismological problems using sgraph program: II-waveform modeling
Abdelwahed, Mohamed F.
2012-09-26
One of the seismological programs to manipulate seismic data is SGRAPH program. It consists of integrated tools to perform advanced seismological techniques. SGRAPH is considered a new system for maintaining and analyze seismic waveform data in a stand-alone Windows-based application that manipulate a wide range of data formats. SGRAPH was described in detail in the first part of this paper. In this part, I discuss the advanced techniques including in the program and its applications in seismology. Because of the numerous tools included in the program, only SGRAPH is sufficient to perform the basic waveform analysis and to solve advanced seismological problems. In the first part of this paper, the application of the source parameters estimation and hypocentral location was given. Here, I discuss SGRAPH waveform modeling tools. This paper exhibits examples of how to apply the SGRAPH tools to perform waveform modeling for estimating the focal mechanism and crustal structure of local earthquakes.
Northern Korean Peninsula 1-D velocity model from surface wave dispersion and full-waveform data
NASA Astrophysics Data System (ADS)
Lee, S. J.; Rhie, J.; Kim, S.; Kang, T. S.; Cho, C.
2016-12-01
Monitoring seismic activities in the northern Korean Peninsula is important not only for understanding the characteristics of earthquakes but also for watching nuclear tests. To better monitor those natural and man-made seismic activities, reliable seismic velocity models are required. However, the seismic velocity structure of the region is not known well due to the lack of available seismic data directly measured in the region. This study presents 1-D velocity models of the region using two different datasets comprised of two-year-long continuous waveform and the 2013 North Korea nuclear test event waveform recorded at stations surrounding the region. Two reference 1-D models for the inland and offshore areas (Western East Sea) were estimated by 1-D inversion of surface wave dispersion measurements from ambient noise cross-correlations of the continuous waveform. To investigate the variations in the velocity models, many 1-D models for the paths between the 2013 nuclear test site and stations in China and South Korea were constructed by forward waveform modeling. The velocity variations are not significant for both models representing the inland and offshore paths, respectively. The 1-D models for the inland paths are similar to the models constructed for the southern Korean Peninsula. Interestingly, waveforms sampling through the offshore paths are not well explained by simple 1-D isotropic models. The preliminary result indicates that there exists radial anisotropy with SH being faster than SV by 3-5% in the upper mantle beneath the offshore northern Korean Peninsula, although further studies are necessary to explain the origin of anisotropy. A proper characterization of propagation effects along the offshore paths would be useful for monitoring future nuclear tests because many seismic stations in the eastern South Korea record waveforms sampling the offshore region from the nuclear test site to those stations.
A Study of Regional Waveform Calibration in the Eastern Mediterranean Region.
NASA Astrophysics Data System (ADS)
di Luccio, F.; Pino, A.; Thio, H.
2002-12-01
We modeled Pnl phases from several moderate magnitude events in the eastern Mediterranean to test methods and to develop path calibrations for source determination. The study region spanning from the eastern part of the Hellenic arc to the eastern Anatolian fault is mostly interested by moderate earthquakes, that can produce relevant damages. The selected area consists of several tectonic environment, which produces increased level of difficulty in waveform modeling. The results of this study are useful for the analysis of regional seismicity and for seismic hazard as well, in particular because very few broadband seismic stations are available in the selected area. The obtained velocity model gives a 30 km crustal tickness and low upper mantle velocities. The applied inversion procedure to determine the source mechanism has been successful, also in terms of discrimination of depth, for the entire range of selected paths. We conclude that using the true calibration of the seismic structure and high quality broadband data, it is possible to determine the seismic source in terms of mechanism, even with a single station.
A radio-frequency sheath model for complex waveforms
Turner, M. M.; Chabert, P.
2014-04-21
Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.
Depths of Intraplate Indian Ocean Earthquakes from Waveform Modeling
NASA Astrophysics Data System (ADS)
Baca, A. J.; Polet, J.
2014-12-01
The Indian Ocean is a region of complex tectonics and anomalous seismicity. The ocean floor in this region exhibits many bathymetric features, most notably the multiple inactive fracture zones within the Wharton Basin and the Ninetyeast Ridge. The 11 April 2012 MW 8.7 and 8.2 strike-slip events that took place in this area are unique because their rupture appears to have extended to a depth where brittle failure, and thus seismic activity, was considered to be impossible. We analyze multiple intraplate earthquakes that have occurred throughout the Indian Ocean to better constrain their focal depths in order to enhance our understanding of how deep intraplate events are occurring and more importantly determine if the ruptures are originating within a ductile regime. Selected events are located within the Indian Ocean away from major plate boundaries. A majority are within the deforming Indo-Australian tectonic plate. Events primarily display thrust mechanisms with some strike-slip or a combination of the two. All events are between MW5.5-6.5. Event selections were handled this way in order to facilitate the analysis of teleseismic waveforms using a point source approximation. From these criteria we gathered a suite of 15 intraplate events. Synthetic seismograms of direct P-waves and depth phases are computed using a 1-D propagator matrix approach and compared with global teleseismic waveform data to determine a best depth for each event. To generate our synthetic seismograms we utilized the CRUST1.0 software, a global crustal model that generates velocity values at the hypocenter of our events. Our waveform analysis results reveal that our depths diverge from the Global Centroid Moment Tensor (GCMT) depths, which underestimate our deep lithosphere events and overestimate our shallow depths by as much as 17 km. We determined a depth of 45km for our deepest event. We will show a comparison of our final earthquake depths with the lithospheric thickness based on
Preliminary Results of Full Seismic Waveform Tomography for Sea of Marmara Region (NW Turkey)
NASA Astrophysics Data System (ADS)
ÇUBUK, Y.; Fichtner, A.; Taymaz, T.
2014-12-01
The Marmara and Northwestern Anatolia regions are known to be a transition zone from the strike-slip tectonics to the extensional tectonics. Although, the Sea of Marmara has been subjected to several active and passive seismic investigations, the accurate knowledge on the heterogeneity in the crust and upper mantle beneath the study area still remains enigmatic. On small-scale tomography problems, seismograms strongly reflect the effects of heterogeneities and the scattering properties of the Earth. Thus, the knowledge of high-resolution seismic imaging with an improved 3D radially anisotropic crustal model of the Northwestern Anatolia will enable better localization of earthquakes, identification of faults as well as the improvement of the seismic hazard assessment. For this purpose, 3D non-linear full waveform inversion methodology has been used to obtain an accurate image of the lithosphere and the upper-most mantle structure over an area of 37.5˚-42˚ N and 25˚-32˚ E and down to a depth of 471 km. The earthquake data were principally obtained from the Kandilli Observatory and Earthquake Research Institute (KOERI) and Earthquake Research Center (AFAD-DAD) database. In addition to this, some of the seismic waveform data extracted from the Hellenic Unified Seismic Network (HUSN) stations that are located within our study region were also used in this study. We have selected and simulated the waveforms of earthquakes with magnitudes Mw ≥ 4 occurred in the period of 2007-2014. In total, 3002 three-component regional seismograms from 95 events were used. The initial 3D earth model for the study region has been implemented from the multi-scale seismic tomography study of Fichtner et al. (2013). The synthetic seismograms were computed with forward modeling of seismic wave propagation by using spectral elements method (SEM). The complete waveforms were filtered at 8-100 seconds. The adjoint method is used to compute sensitivity kernels. The differences between
A complete waveform model for compact binaries on eccentric orbits
NASA Astrophysics Data System (ADS)
George, Daniel; Huerta, Eliu; Kumar, Prayush; Agarwal, Bhanu; Schive, Hsi-Yu; Pfeiffer, Harald; Chu, Tony; Boyle, Michael; Hemberger, Daniel; Kidder, Lawrence; Scheel, Mark; Szilagyi, Bela
2017-01-01
We present a time domain waveform model that describes the inspiral, merger and ringdown of compact binary systems whose components are non-spinning, and which evolve on orbits with low to moderate eccentricity. We show that this inspiral-merger-ringdown waveform model reproduces the effective-one-body model for black hole binaries with mass-ratios between 1 to 15 in the zero eccentricity limit over a wide range of the parameter space under consideration. We use this model to show that the gravitational wave transients GW150914 and GW151226 can be effectively recovered with template banks of quasicircular, spin-aligned waveforms if the eccentricity e0 of these systems when they enter the aLIGO band at a gravitational wave frequency of 14 Hz satisfies e0GW 150914 <= 0 . 15 and e0GW 151226 <= 0 . 1 .
Synchronous Generator Model Parameter Estimation Based on Noisy Dynamic Waveforms
NASA Astrophysics Data System (ADS)
Berhausen, Sebastian; Paszek, Stefan
2016-01-01
In recent years, there have occurred system failures in many power systems all over the world. They have resulted in a lack of power supply to a large number of recipients. To minimize the risk of occurrence of power failures, it is necessary to perform multivariate investigations, including simulations, of power system operating conditions. To conduct reliable simulations, the current base of parameters of the models of generating units, containing the models of synchronous generators, is necessary. In the paper, there is presented a method for parameter estimation of a synchronous generator nonlinear model based on the analysis of selected transient waveforms caused by introducing a disturbance (in the form of a pseudorandom signal) in the generator voltage regulation channel. The parameter estimation was performed by minimizing the objective function defined as a mean square error for deviations between the measurement waveforms and the waveforms calculated based on the generator mathematical model. A hybrid algorithm was used for the minimization of the objective function. In the paper, there is described a filter system used for filtering the noisy measurement waveforms. The calculation results of the model of a 44 kW synchronous generator installed on a laboratory stand of the Institute of Electrical Engineering and Computer Science of the Silesian University of Technology are also given. The presented estimation method can be successfully applied to parameter estimation of different models of high-power synchronous generators operating in a power system.
Full waveform modelling and misfit calculation using the VERCE platform
NASA Astrophysics Data System (ADS)
Garth, Thomas; Spinuso, Alessandro; Casarotti, Emanuele; Magnoni, Federica; Krischner, Lion; Igel, Heiner; Schwichtenberg, Horst; Frank, Anton; Vilotte, Jean-Pierre; Rietbrock, Andreas
2016-04-01
In recent years the increasing resolution of seismic imagining by full waveform inversion has opened new research perspectives and practices. These methods rely on harnessing the computational power of large supercomputers and new storage capabilities, to run large parallel codes to simulate the seismic wave field in three-dimensional geological settings. The VERCE platform is designed to make these full waveform techniques accessible to a far wider spectrum of the seismological community. VERCE empowers a broad base of seismology researchers to harvest the new opportunities provided by well-established high-performance wave simulation codes such as SPECFEM3D. It meets a range of seismic research needs by eliminating the technical difficulties associated with using these codes, allowing users to focus on their research questions. VERCE delivers this power to seismologists through its science gateway, supporting wave simulation codes on each of the provided computing resources. Users can design their waveform simulation scenarios making use of a library of pre-loaded meshes and velocity models, and services for selecting earthquake focal mechanisms, seismic stations and recorded waveforms from existing catalogues, such as the GCMT catalogue, and FDSN data sources. They can also supply their own mesh, velocity model, earthquake catalogue and seismic observations. They can submit the simulations onto different computing resources, where VERCE provides codes that are tuned and supported for those resources. The simulations can currently be run on a range of European supercomputers in the PRACE network, including superMUC at LRZ, GALILEO at CINECA and on selected resources like Drachenfels at SCAI and within the EGI network. The gateway automates and looks after all these stages, but supplies seismologists with a provenance system that allows them to manage a large series of runs, review progress, and explore the results. The platform automates misfit analysis between
Waveform modeling the deep slab beneath northernmost Nevada
NASA Astrophysics Data System (ADS)
Helmberger, D. V.; Sun, D.
2011-12-01
The interactions between subducted slab and transition zone are crucial issues in dynamic modeling. Previous mantle convection studies have shown that various viscosity structures can result in various slab shape, width, and edge sharpness. Recent tomographic images based on USArray data reveals strong multi-scale heterogeneous upper mantle beneath western US. Among those features, a slab-like fast anomaly extends from 300 to 600 km depth below Nevada and western Utah, which was suggested as a segmented chunk of the Farallon slab. But we still missing key information about the details of this structure and whether this structure flatten outs in the transition zone, where various tomographic models display inconsistent images. The study of multipathing and waveform broadening around sharp features have been proved a efficient way to study such features. Here, we use both P and S waveform data from High Lava Plains seismic experiments and USArray to produce a detailed image. If we amplify the Schmandt and Humphreys [2010] 's S-wave tomography model by 1.5, we can produce excellent travel-time fits. But the waveform distortions are not as strong as those observed in data for events coming from the southeast, which suggest a much sharper anomaly. The waveform broadening features are not observed for events arriving from northwestern. By fitting the SH waveform data, we suggest that this slab-like structure dips ~35° to the southeast, extending to a depth near 660 km with a velocity increase of about 5 per cent. To generate corresponding P model, we adapt the SH wave model and scale the model using a suite of R (=dlnVs/dlnVp) values. We find that synthetics from the model with R ≈ 2 can fit the observed data, which confirms the segmented slab interpretation of this high velocity anomaly.
A study of regional waveform calibration in the eastern Mediterranean
NASA Astrophysics Data System (ADS)
Di Luccio, F.; Pino, N. A.; Thio, H. K.
2003-06-01
We modeled P nl phases from several moderate magnitude earthquakes in the eastern Mediterranean to test methods and develop path calibrations for determining source parameters. The study region, which extends from the eastern part of the Hellenic arc to the eastern Anatolian fault, is dominated by moderate earthquakes that can produce significant damage. Our results are useful for analyzing regional seismicity as well as seismic hazard, because very few broadband seismic stations are available in the selected area. For the whole region we have obtained a single velocity model characterized by a 30 km thick crust, low upper mantle velocities and a very thin lid overlaying a distinct low velocity layer. Our preferred model proved quite reliable for determining focal mechanism and seismic moment across the entire range of selected paths. The source depth is also well constrained, especially for moderate earthquakes.
Effects of waveform model systematics on the interpretation of GW150914
NASA Astrophysics Data System (ADS)
Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Ananyeva, A.; Anderson, S. B.; Anderson, W. G.; Appert, S.; Arai, K.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; E Barclay, S.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Beer, C.; Bejger, M.; Belahcene, I.; Belgin, M.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Boer, M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; E Brau, J.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; E Broida, J.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, H.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y.; Cheng, H.-P.; Chincarini, A.; Chiummo, A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M., Jr.; Conti, L.; Cooper, S. J.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Covas, P. B.; E Cowan, E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; E Creighton, J. D.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cullen, T. J.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davies, G. S.; Davis, D.; Daw, E. J.; Day, B.; Day, R.; De, S.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devenson, J.; Devine, R. C.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Doctor, Z.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorrington, I.; Douglas, R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; E Dwyer, S.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Etienne, Z.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr, B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Fernández Galiana, A.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fong, H.; Forsyth, S. S.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.; Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky, M. L.; E Gossan, S.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; E Gushwa, K.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; E Holz, D.; Hopkins, P.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kéfélian, F.; Keitel, D.; Kelley, D. B.; Kennedy, R.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, Whansun; Kim, W.; Kim, Y.-M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kirchhoff, R.; Kissel, J. S.; Klein, B.; Kleybolte, L.; Klimenko, S.; Koch, P.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lang, R. N.; Lange, J.; Lantz, B.; Lanza, R. K.; Lartaux-Vollard, A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lehmann, J.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Liu, J.; Lockerbie, N. A.; Lombardi, A. L.; London, L. T.; E Lord, J.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lovelace, G.; Lück, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macfoy, S.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; E McClelland, D.; McCormick, S.; McGrath, C.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; E Mikhailov, E.; Milano, L.; Miller, A. L.; Miller, A.; Miller, B. B.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Muniz, E. A. M.; Murray, P. G.; Mytidis, A.; Napier, K.; Nardecchia, I.; Naticchioni, L.; Nelemans, G.; Nelson, T. J. N.; Neri, M.; Nery, M.; Neunzert, A.; Newport, J. M.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; E Pace, A.; Page, J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perez, C. J.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Pratt, J. W. W.; Predoi, V.; Prestegard, T.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Rhoades, E.; Ricci, F.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sampson, L. M.; Sanchez, E. J.; Sandberg, V.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Scheuer, J.; Schmidt, E.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Schwalbe, S. G.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Setyawati, Y.; Shaddock, D. A.; Shaffer, T. J.; Shahriar, M. S.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, B.; Smith, J. R.; E Smith, R. J.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Spencer, A. P.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stevenson, S. P.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; E Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Taracchini, A.; Taylor, R.; Theeg, T.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tippens, T.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tomlinson, C.; Tonelli, M.; Tornasi, Z.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tse, M.; Tso, R.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Varma, V.; Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Viets, A. D.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; E Wade, L.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Watchi, J.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Whittle, C.; Williams, D.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Worden, J.; Wright, J. L.; Wu, D. S.; Wu, G.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, Hang; Yu, Haocun; Yvert, M.; Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.; Zhu, X. J.; E Zucker, M.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration; Boyle, M.; Chu, T.; Hemberger, D.; Hinder, I.; E Kidder, L.; Ossokine, S.; Scheel, M.; Szilagyi, B.; Teukolsky, S.; Vano Vinuales, A.
2017-05-01
Parameter estimates of GW150914 were obtained using Bayesian inference, based on three semi-analytic waveform models for binary black hole coalescences. These waveform models differ from each other in their treatment of black hole spins, and all three models make some simplifying assumptions, notably to neglect sub-dominant waveform harmonic modes and orbital eccentricity. Furthermore, while the models are calibrated to agree with waveforms obtained by full numerical solutions of Einstein’s equations, any such calibration is accurate only to some non-zero tolerance and is limited by the accuracy of the underlying phenomenology, availability, quality, and parameter-space coverage of numerical simulations. This paper complements the original analyses of GW150914 with an investigation of the effects of possible systematic errors in the waveform models on estimates of its source parameters. To test for systematic errors we repeat the original Bayesian analysis on mock signals from numerical simulations of a series of binary configurations with parameters similar to those found for GW150914. Overall, we find no evidence for a systematic bias relative to the statistical error of the original parameter recovery of GW150914 due to modeling approximations or modeling inaccuracies. However, parameter biases are found to occur for some configurations disfavored by the data of GW150914: for binaries inclined edge-on to the detector over a small range of choices of polarization angles, and also for eccentricities greater than ˜0.05. For signals with higher signal-to-noise ratio than GW150914, or in other regions of the binary parameter space (lower masses, larger mass ratios, or higher spins), we expect that systematic errors in current waveform models may impact gravitational-wave measurements, making more accurate models desirable for future observations.
NASA Astrophysics Data System (ADS)
Wang, Tao; Revenaugh, Justin; Song, Xiaodong
2014-06-01
Subduction plays a fundamental role in dynamics of the mantle convection and in material circulations of the Earth's interior. Slabs have been imaged to subduct near horizontally in the transition zone (TZ) beneath the Northeast Asia in seismic tomography. Triplication waveform modeling is an effective tool to study the detailed seismic structure in the TZ. However, TZ triplication modeling has traditionally relied on 1-D models. In this study, we use the spectral element method to explore influences of 2-D/3-D slab structure on TZ triplication waveforms and to model, for the first time, the slab and TZ structures beneath the Northeast Asia. Synthetic tests suggest that, for a subduction zone earthquake, slab structure can have important influences on TZ triplication waveforms and that, even in a narrow azimuth range, the effects from 2-D/3-D slab structure on the wave propagation can lead to erroneous conclusions with 1-D modeling. Our data are high-quality triplicated SH waveforms (at distances of 10°-32°) from a deep event (below 410 km discontinuity) in the Pacific subducting slab. Our 2-D/3-D waveform modeling results suggest that a simple model of the subducting slab (+5% high-velocity anomaly and 100 km thick down to 560 km) but normal below 560 km can match most of the observed waveforms remarkably well. The bottom of the TZ of the sampling region (north of the Yellow Sea) contains a patch of very slow anomaly. The results indicate that subhorizontal slab above the 660 discontinuity is not everywhere beneath Northeast Asia and the subducting slab is not everywhere continuous to the bottom of the TZ. Compared with the traditional 1-D modeling, our new 2-D/3-D approach provides better fits to the data and allows us to constrain the slab geometry and to separate TZ structure from slab structure
Modelling Sensor and Target effects on LiDAR Waveforms
NASA Astrophysics Data System (ADS)
Rosette, J.; North, P. R.; Rubio, J.; Cook, B. D.; Suárez, J.
2010-12-01
The aim of this research is to explore the influence of sensor characteristics and interactions with vegetation and terrain properties on the estimation of vegetation parameters from LiDAR waveforms. This is carried out using waveform simulations produced by the FLIGHT radiative transfer model which is based on Monte Carlo simulation of photon transport (North, 1996; North et al., 2010). The opportunities for vegetation analysis that are offered by LiDAR modelling are also demonstrated by other authors e.g. Sun and Ranson, 2000; Ni-Meister et al., 2001. Simulations from the FLIGHT model were driven using reflectance and transmittance properties collected from the Howland Research Forest, Maine, USA in 2003 together with a tree list for a 200m x 150m area. This was generated using field measurements of location, species and diameter at breast height. Tree height and crown dimensions of individual trees were calculated using relationships established with a competition index determined for this site. Waveforms obtained by the Laser Vegetation Imaging Sensor (LVIS) were used as validation of simulations. This provided a base from which factors such as slope, laser incidence angle and pulse width could be varied. This has enabled the effect of instrument design and laser interactions with different surface characteristics to be tested. As such, waveform simulation is relevant for the development of future satellite LiDAR sensors, such as NASA’s forthcoming DESDynI mission (NASA, 2010), which aim to improve capabilities of vegetation parameter estimation. ACKNOWLEDGMENTS We would like to thank scientists at the Biospheric Sciences Branch of NASA Goddard Space Flight Center, in particular to Jon Ranson and Bryan Blair. This work forms part of research funded by the NASA DESDynI project and the UK Natural Environment Research Council (NE/F021437/1). REFERENCES NASA, 2010, DESDynI: Deformation, Ecosystem Structure and Dynamics of Ice. http
Analysis of ICESat/GLAS waveform data for characterizing forests in a hilly region
NASA Astrophysics Data System (ADS)
Hilbert, Claudia; Schmullius, Christiane; Zink, Manfred
2011-10-01
ICESat/GLAS data for a temperate forest in a hilly region were analysed regarding the potential to retrieve maximum canopy height using a direct approach. The GLAS height was derived by calculating the range of the waveform Signal Begin and the Ground Peak. The comparison with an inventory data base and airborne lidar based heights revealed that the GLAS height overestimates the reference heights by on average 5 m and 7 m, respectively (Std=6 m and Std=5 m). The GLAS waveforms were further investigated regarding the canopy structure and the ground surface topography. It was found that the waveforms are most influenced by the ground surface topography. The topography clearly affects the waveform shape and therefore also the accuracy of the GLAS height estimation. Waveforms corresponding to footprints with a mean slope up to 10° have a high potential to derive tree height. The correlation between the GLAS and reference heights is still fair for waveforms of moderate slope 10-15°. Higher slopes clearly challenge the analysis of the waveform structure and the derivation of forest parameters.
multi-scale approaches for full waveform difference inversion and tomographic model analysis
NASA Astrophysics Data System (ADS)
Yuan, Y.; Simons, F. J.; Luo, Y.
2012-12-01
Tomographic Earth models are solutions to mixed-determined inverse problems, which are formulated to minimize some measure of difference between synthetics and observed data. Typically, the measurement takes the form of a cross-correlation travel-time difference, or it might be the norm of the difference between the entire waveforms, in which case every wiggle is being used to extract information from the data. Full-waveform difference tomography suffers from a slow convergence rate and a danger of converging to local minima. In this presentation, we explore several routes to improving full-waveform inversion strategies for global and regional seismic tomography. First, we will discuss a wavelet-based multi-scale approach that works progressively from low to higher scales, step-by-step involving more details of the waveform. Second, we will discuss a hybrid misfit strategy that combines cross-correlation traveltime and waveform-difference measurements. We will discuss the making of multiscale sensitivity kernels using wavelet decompositions of the seismogram. Lastly, we move to the model space to conduct a multi-scale analysis of global tomographic models using a class of 3-D spherical wavelet bases that are implemented on the ``cubed ball'', the 3-D extension of the ``cubed sphere''. Using this novel transform we study the sparsity of global seismic tomographic models via thresholded reconstruction, and characterize the relative importance and patterns of features in the Earth models via individual and cumulative reconstructions of their wavelet coefficients. Whether on the side of the data, the sensitivity kernels, or in the model space, tomographic inverse problems have much to gain from the flexibility of the wavelet decomposition in one, two and three dimensions, and this on a global, regional or exploration scale, as we show by example. Full waveform difference inversion. The first figure shows our target model with two anomalous regions. The red stars
Coupling hydrodynamic and wave propagation modeling for waveform modeling of SPE.
NASA Astrophysics Data System (ADS)
Larmat, C. S.; Steedman, D. W.; Rougier, E.; Delorey, A.; Bradley, C. R.
2015-12-01
The goal of the Source Physics Experiment (SPE) is to bring empirical and theoretical advances to the problem of detection and identification of underground nuclear explosions. This paper presents effort to improve knowledge of the processes that affect seismic wave propagation from the hydrodynamic/plastic source region to the elastic/anelastic far field thanks to numerical modeling. The challenge is to couple the prompt processes that take place in the near source region to the ones taking place later in time due to wave propagation in complex 3D geologic environments. In this paper, we report on results of first-principles simulations coupling hydrodynamic simulation codes (Abaqus and CASH), with a 3D full waveform propagation code, SPECFEM3D. Abaqus and CASH model the shocked, hydrodynamic region via equations of state for the explosive, borehole stemming and jointed/weathered granite. LANL has been recently employing a Coupled Euler-Lagrange (CEL) modeling capability. This has allowed the testing of a new phenomenological model for modeling stored shear energy in jointed material. This unique modeling capability has enabled highfidelity modeling of the explosive, the weak grout-filled borehole, as well as the surrounding jointed rock. SPECFEM3D is based on the Spectral Element Method, a direct numerical method for full waveform modeling with mathematical accuracy (e.g. Komatitsch, 1998, 2002) thanks to its use of the weak formulation of the wave equation and of high-order polynomial functions. The coupling interface is a series of grid points of the SEM mesh situated at the edge of the hydrodynamic code domain. Displacement time series at these points are computed from output of CASH or Abaqus (by interpolation if needed) and fed into the time marching scheme of SPECFEM3D. We will present validation tests and waveforms modeled for several SPE tests conducted so far, with a special focus on effect of the local topography.
Assessing waveform predictions of recent three-dimensional velocity models of the Tibetan Plateau
NASA Astrophysics Data System (ADS)
Bao, Xueyang; Shen, Yang
2016-04-01
Accurate velocity models are essential for both the determination of earthquake locations and source moments and the interpretation of Earth structures. With the increasing number of three-dimensional velocity models, it has become necessary to assess the models for accuracy in predicting seismic observations. Six models of the crustal and uppermost mantle structures in Tibet and surrounding regions are investigated in this study. Regional Rayleigh and Pn (or Pnl) waveforms from two ground truth events, including one nuclear explosion and one natural earthquake located in the study area, are simulated by using a three-dimensional finite-difference method. Synthetics are compared to observed waveforms in multiple period bands of 20-75 s for Rayleigh waves and 1-20 s for Pn/Pnl waves. The models are evaluated based on the phase delays and cross-correlation coefficients between synthetic and observed waveforms. A model generated from full-wave ambient noise tomography best predicts Rayleigh waves throughout the data set, as well as Pn/Pnl waves traveling from the Tarim Basin to the stations located in central Tibet. In general, the models constructed from P wave tomography are not well suited to predict Rayleigh waves, and vice versa. Possible causes of the differences between observed and synthetic waveforms, and frequency-dependent variations of the "best matching" models with the smallest prediction errors are discussed. This study suggests that simultaneous prediction for body and surface waves requires an integrated velocity model constructed with multiple seismic waveforms and consideration of other important properties, such as anisotropy.
NASA Astrophysics Data System (ADS)
Blackman, Jonathan; Field, Scott; Galley, Chad; Hemberger, Daniel; Scheel, Mark; Schmidt, Patricia; Smith, Rory
2017-01-01
Extracting astrophysical parameters and testing general relativity from gravitational wave observations of binary black hole mergers requires high-fidelity signal predictions. The effective-one-body model and phenomenological waveform models have been shown to work well for a subset of the possible parameter space. They could be insufficiently accurate for estimating the parameters of a loud gravitational wave detection in other regions of the parameter space. Numerical relativity (NR) surrogate models attempt to rapidly and accurately interpolate the waveforms from a set of NR simulations over a subset of parameter space. Using the Spectral Einstein Code (SpEC), we have built NR surrogate models for precessing binaries with a restricted spin direction on the smaller black hole, and are actively working on extending this to the full 7d parameter space of non-eccentric binaries. The NR surrogate models typically perform an order of magnitude better than other waveform models when compared to NR waveforms which were not included in the surrogate training set, and can be used in gravitational wave parameter estimation.
Modeling Magnetic Core Loss for Sinusoidal Waveforms
2008-06-01
Manganese Zinc (MnZn) Power Ferrites between 100 kHz to 500 kHz CPL data is empirically fit to the PLE given in Equation 3, the values of the curve...calculation. The frequency range used in this experiment was 100 to 700 kHz and the material used was 3F3. 3F3 is a Manganese Zinc power ferrite ...reported that compares these models to actual Power Ferrite data. In addition, three components used in several of CPL empirical equations have been
Modeling Gravitational Radiation Waveforms from Black Hole Mergers
NASA Technical Reports Server (NTRS)
Baker, J. G.; Centrelia, J. M.; Choi, D.; Koppitz, M.; VanMeter, J.
2006-01-01
Gravitational radiation from merging binary black hole systems is anticipated as a key source for gravitational wave observations. Ground-based instruments, such as the Laser Interferometer Gravitational-wave Observatory (LIGO) may observe mergers of stellar-scale black holes, while the space-based Laser Interferometer Space Antenna (LISA) observatory will be sensitive to mergers of massive galactic-center black holes over a broad range of mass scales. These cataclysmic events may emit an enormous amount of energy in a brief time. Gravitational waves from comparable mass mergers carry away a few percent of the system's mass-energy in just a few wave cycles, with peak gravitational wave luminosities on the order of 10^23 L_Sun. Optimal analysis and interpretation of merger observation data will depend on developing a detailed understanding, based on general relativistic modeling, of the radiation waveforms. We discuss recent progress in modeling radiation from equal mass mergers using numerical simulations of Einstein's gravitational field equations, known as numerical relativity. Our simulations utilize Adaptive Mesh Refinement (AMR) to allow high-resolution near the black holes while simultaneously keeping the outer boundary of the computational domain far from the black holes, and making it possible to read out gravitational radiation waveforms in the weak-field wave zone. We discuss the results from simulations beginning with the black holes orbiting near the system's innermost stable orbit, comparing the recent simulations with earlier "Lazarus" waveform estimates based on an approximate hybrid numerical/perturbative technique.
Modeling Gravitational Radiation Waveforms from Black Hole Mergers
NASA Technical Reports Server (NTRS)
Baker, J. G.; Centrelia, J. M.; Choi, D.; Koppitz, M.; VanMeter, J.
2006-01-01
Gravitational radiation from merging binary black hole systems is anticipated as a key source for gravitational wave observations. Ground-based instruments, such as the Laser Interferometer Gravitational-wave Observatory (LIGO) may observe mergers of stellar-scale black holes, while the space-based Laser Interferometer Space Antenna (LISA) observatory will be sensitive to mergers of massive galactic-center black holes over a broad range of mass scales. These cataclysmic events may emit an enormous amount of energy in a brief time. Gravitational waves from comparable mass mergers carry away a few percent of the system's mass-energy in just a few wave cycles, with peak gravitational wave luminosities on the order of 10^23 L_Sun. Optimal analysis and interpretation of merger observation data will depend on developing a detailed understanding, based on general relativistic modeling, of the radiation waveforms. We discuss recent progress in modeling radiation from equal mass mergers using numerical simulations of Einstein's gravitational field equations, known as numerical relativity. Our simulations utilize Adaptive Mesh Refinement (AMR) to allow high-resolution near the black holes while simultaneously keeping the outer boundary of the computational domain far from the black holes, and making it possible to read out gravitational radiation waveforms in the weak-field wave zone. We discuss the results from simulations beginning with the black holes orbiting near the system's innermost stable orbit, comparing the recent simulations with earlier "Lazarus" waveform estimates based on an approximate hybrid numerical/perturbative technique.
Assessment of brain compliance using ICP waveform analysis in water intoxication rat model.
Oshio, Kotaro; Onodera, Hidetaka; Uchida, Masashi; Tanaka, Yuichiro; Hashimoto, Takuo
2013-01-01
Intracranial pressure (ICP) monitoring has been used widely for patients with intracranial hypertension. However, the data of mean ICP do not reflect various brain conditions correctly. Therefore, we performed ICP -waveform analysis to assess brain compliance. Data for ICP -waveform analysis were obtained by stereotactic intraventricle puncture. ICP waveform is expressed as a three-phase wave. Analyzed differential waveforms in a water intoxication model and continuous infusion models were evaluated respectively. In the water intoxication models, the second wave (P2) known to reflect compliance is elevated. ICP waveform analysis will be valuable for the assessment of the pathological condition of the brain.
Finite Element and Plate Theory Modeling of Acoustic Emission Waveforms
NASA Technical Reports Server (NTRS)
Prosser, W. H.; Hamstad, M. A.; Gary, J.; OGallagher, A.
1998-01-01
A comparison was made between two approaches to predict acoustic emission waveforms in thin plates. A normal mode solution method for Mindlin plate theory was used to predict the response of the flexural plate mode to a point source, step-function load, applied on the plate surface. The second approach used a dynamic finite element method to model the problem using equations of motion based on exact linear elasticity. Calculations were made using properties for both isotropic (aluminum) and anisotropic (unidirectional graphite/epoxy composite) materials. For simulations of anisotropic plates, propagation along multiple directions was evaluated. In general, agreement between the two theoretical approaches was good. Discrepancies in the waveforms at longer times were caused by differences in reflections from the lateral plate boundaries. These differences resulted from the fact that the two methods used different boundary conditions. At shorter times in the signals, before reflections, the slight discrepancies in the waveforms were attributed to limitations of Mindlin plate theory, which is an approximate plate theory. The advantages of the finite element method are that it used the exact linear elasticity solutions, and that it can be used to model real source conditions and complicated, finite specimen geometries as well as thick plates. These advantages come at a cost of increased computational difficulty, requiring lengthy calculations on workstations or supercomputers. The Mindlin plate theory solutions, meanwhile, can be quickly generated on personal computers. Specimens with finite geometry can also be modeled. However, only limited simple geometries such as circular or rectangular plates can easily be accommodated with the normal mode solution technique. Likewise, very limited source configurations can be modeled and plate theory is applicable only to thin plates.
Complete waveform model for compact binaries on eccentric orbits
NASA Astrophysics Data System (ADS)
Huerta, E. A.; Kumar, Prayush; Agarwal, Bhanu; George, Daniel; Schive, Hsi-Yu; Pfeiffer, Harald P.; Haas, Roland; Ren, Wei; Chu, Tony; Boyle, Michael; Hemberger, Daniel A.; Kidder, Lawrence E.; Scheel, Mark A.; Szilagyi, Bela
2017-01-01
We present a time domain waveform model that describes the inspiral, merger and ringdown of compact binary systems whose components are nonspinning, and which evolve on orbits with low to moderate eccentricity. The inspiral evolution is described using third-order post-Newtonian equations both for the equations of motion of the binary, and its far-zone radiation field. This latter component also includes instantaneous, tails and tails-of-tails contributions, and a contribution due to nonlinear memory. This framework reduces to the post-Newtonian approximant TaylorT4 at third post-Newtonian order in the zero-eccentricity limit. To improve phase accuracy, we also incorporate higher-order post-Newtonian corrections for the energy flux of quasicircular binaries and gravitational self-force corrections to the binding energy of compact binaries. This enhanced prescription for the inspiral evolution is combined with a fully analytical prescription for the merger-ringdown evolution constructed using a catalog of numerical relativity simulations. We show that this inspiral-merger-ringdown waveform model reproduces the effective-one-body model of Ref. [Y. Pan et al., Phys. Rev. D 89, 061501 (2014)., 10.1103/PhysRevD.89.061501] for quasicircular black hole binaries with mass ratios between 1 to 15 in the zero-eccentricity limit over a wide range of the parameter space under consideration. Using a set of eccentric numerical relativity simulations, not used during calibration, we show that our new eccentric model reproduces the true features of eccentric compact binary coalescence throughout merger. We use this model to show that the gravitational-wave transients GW150914 and GW151226 can be effectively recovered with template banks of quasicircular, spin-aligned waveforms if the eccentricity e0 of these systems when they enter the aLIGO band at a gravitational-wave frequency of 14 Hz satisfies e0GW 150914≤0.15 and e0GW 151226≤0.1 . We also find that varying the spin
Multi-scale full waveform inversion using teleseismic and regional data sets
NASA Astrophysics Data System (ADS)
Fichtner, A.; Trampert, J.; Villasenor, A.; Saygin, E.; Taymaz, T.
2011-12-01
We present the first results of a long-term project that aims at the construction of a comprehensive seismic model of the European upper mantle, that describes 3D structural variations with a lateral resolution ranging from ≈1000 km in poorly covered regions to ≈10 km in areas where dense regional data sets are available. Our method is based on a full waveform inversion that combines spectral-element simulations of seismic wave propagation with adjoint techniques. This approach ensures the high accuracy of synthetic seismograms, it avoids crustal corrections, and it allows for the simultaneous inversion for crustal and mantle structure. As data we use complete three-component recordings from permanent stations, complemented by data from very dense regional arrays such as IberArray and the Turkish broadband network. To model regional data at short periods, we partition the computational domain into a set of nested sub-domains. While the grid spacing is largest in the continent-wide domain, it can be reduced substantially within smaller sub-domains, comprising, for instance, the Iberian Peninsula or Turkey. The sub-domains are linked via one single structural model with a resolution-adaptive parameterisation. To upscale small-scale structure from finely-parameterised parts of the model onto the coarse grid of the continent-wide domain, we use non-periodic homogenisation. This variant of "divide and conquer" leads to a multi-scale model that exhibits great detail in the most densely covered regions. Preliminary results already reveal the properties of smaller-scale features such as the Hellenic slab and the Pannonian basin. One of the most prominent structures found in the model is the Iceland plume, with unexpectedly low S velocities (-8 % at 200 km depth) that suggest the presence of partial melt or fluids.
NASA Astrophysics Data System (ADS)
Monteiller, Vadim; Beller, Stephen; Operto, Stephane; Virieux, Jean
2015-04-01
The current development of dense seismic arrays and high performance computing make feasible today application of full-waveform inversion (FWI) on teleseismic data for high-resolution lithospheric imaging. In teleseismic configuration, the source is often considered to first order as a planar wave that impinges the base of the lithospheric target located below the receiver array. Recently, injection methods coupling global propagation in 1D or axisymmetric earth model with regional 3D methods (Discontinuous Galerkin finite element methods, Spectral elements methods or finite differences) allow us to consider more realistic teleseismic phases. Those teleseismic phases can be propagated inside 3D regional model in order to exploit not only the forward-scattered waves propagating up to the receiver but also second-order arrivals that are back-scattered from the free-surface and the reflectors before their recordings on the surface. However, those computation are performed assuming simple global model. In this presentation, we review some key specifications that might be considered for mitigating the effect on FWI of heterogeneities situated outside the regional domain. We consider synthetic models and data computed using our recently developed hybrid method AxiSEM/SEM. The global simulation is done by AxiSEM code which allows us to consider axisymmetric anomalies. The 3D regional computation is performed by Spectral Element Method. We investigate the effect of external anomalies on the regional model obtained by FWI when one neglects them by considering only 1D global propagation. We also investigate the effect of the source time function and the focal mechanism on results of the FWI approach.
Assessing waveform predictions of recent three-dimensional velocity models of Tibet
NASA Astrophysics Data System (ADS)
Bao, X.; Shen, Y.
2015-12-01
High-resolution tomographic models are essential for understanding the physical and compositional properties in the lithosphere and obtaining accurate earthquake source locations and moment tensors. Yet, there are significant disagreements in recent three-dimensional velocity models of the crust and uppermost mantle in Tibet. Question also remains as to whether models constructed from one type of seismic waves (body or surface waves) can be used to predict travel times and waveforms of another. In this study, six global or regional models are selected for Tibet, most of which became publically available in the past five years. A three-dimensional finite-difference method in the spherical coordinates is applied to simulate full-wave propagation of regional Pn (with periods longer than 1 second) and Rayleigh waves (20-75 s period) for ground-truth events located at regional distances. The models are evaluated based on the phase delays and cross-correlation coefficients between synthetic and observed waveforms. A model generated from full-wave ambient noise tomography by Shen and Zhang (2012) consistently produces the best predictions for Rayleigh waves throughout the dataset and the Pn waves for the paths from the Tarim Basin to central Tibet. LITHO1.0, inverted from surface wave dispersions, shows a relatively stable but intermediate performance in predicting Pn and Rayleigh waves. None of the models provide the best matches to both waves throughout the region. Furthermore, the models constructed from surface waves are not well suited to predict Pn, and vice versa. We attribute this mainly to lack of accurate constraints on radial anisotropy and Vp/Vs ratios in the upper mantle, and Moho topography. We conclude that simultaneous prediction for P, S, and surface waves requires an integrated velocity model constructed with multiple seismic waveforms and consideration of other important properties, such as anisotropy and attenuation.
NASA Astrophysics Data System (ADS)
Cho, Hee-Suk
2015-11-01
The phenomenological gravitational waveform models, which we refer to as PhenomA, PhenomB, and PhenomC, generate full inspiral, merger, and ringdown (IMR) waveforms of coalescing binary back holes (BBHs). These models are defined in the Fourier domain, thus can be used for fast matched filtering in the gravitational wave search. PhenomA has been developed for nonspinning BBH waveforms, while PhenomB and PhenomC were designed to model the waveforms of BBH systems with nonprecessing (aligned) spins, but can also be used for nonspinning systems. In this work, we study the validity of the phenomenological models for nonspinning BBH searches at low masses, {m}{1,2}≥slant 4{M}⊙ and {m}1+{m}2\\equiv M≤slant 30{M}⊙ , with Advanced LIGO. As our complete signal waveform model, we adopt EOBNRv2, which is a time-domain IMR waveform model. To investigate the search efficiency of the phenomenological template models, we calculate fitting factors (FFs) by exploring overlap surfaces. We find that only PhenomC is valid to obtain FFs better than 0.97 in the mass range of M\\lt 15{M}⊙ . Above 15{M}⊙ , PhenomA is most efficient in symmetric mass region, PhenomB is most efficient in highly asymmetric mass region, and PhenomC is most efficient in the intermediate region. Specifically, we propose an effective phenomenological template family that can be constructed by employing the phenomenological models in four subregions individually. We find that FFs of the effective templates are better than 0.97 in our entire mass region and mostly greater than 0.99.
Waveform Modeling Constraints on the South African Superplume
NASA Astrophysics Data System (ADS)
Helmberger, D.; Ni, S.
2003-12-01
Tomographic studies of the lower mantle structure beneath South Africa reveal large-scale slow velocities from the core-mantle-boundary (CMB) to about a depth of 1500 km. Predicted SKS delay patterns (up to 3 sec) for some of these models fit observations (South African Array Data) quite well except for magnitude level, explaining less than ((1)/(2)) the anomaly. Moreover, the sharpness in travel time offsets and waveform complications require nearly vertical walls separating the anomalous structure from the normal PREM mantle. We present numerous record sections along with 2D and 3D synthetics displaying multi-pathing of arrivals (Sdiff, SKS, SKKS, S and ScS) based on our previous plume model. This ridge model has a crescent shape with one apex beneath the Indian Ocean (Kerguelen) with the other beneath the mid-Atlantic (Cape Verde). The structure extends upward through the lower mantle similar to Grand's model but with an average uniform velocity decrease of about 3% relative to PREM, although there is some evidence for a still slower core or upward doming near the middle of the structure. Some record sections fit the observed waveform complexity better than our standard model by injecting a thin (50 km wide) thermal boundary layer along the walls with depressed velocities. We have not found any evidences for ULVZ's beneath the main structure but ample evidence at some locations near the edges. We also analyzed Pdiff and the differentials of (PcP-P) along the same great circle paths (same events). The P-velocity is not very anomalous, perhaps -.5%, arguing for a chemical origin.
NASA Astrophysics Data System (ADS)
Kotchenova, Svetlana Y.; Shabanov, Nikolay V.; Knyazikhin, Yuri; Davis, Anthony B.; Dubayah, Ralph; Myneni, Ranga B.
2003-08-01
Large footprint waveform-recording laser altimeters (lidars) have demonstrated a potential for accurate remote sensing of forest biomass and structure, important for regional and global climate studies. Currently, radiative transfer analyses of lidar data are based on the simplifying assumption that only single scattering contributes to the return signal, which may lead to errors in the modeling of the lower portions of recorded waveforms in the near-infrared spectrum. In this study we apply time-dependent stochastic radiative transfer (RT) theory to model the propagation of lidar pulses through forest canopies. A time-dependent stochastic RT equation is formulated and solved numerically. Such an approach describes multiple scattering events, allows for realistic representation of forest structure including foliage clumping and gaps, simulates off-nadir and multiangular observations, and has the potential to provide better approximations of return waveforms. The model was tested with field data from two conifer forest stands (southern old jack pine and southern old black spruce) in central Canada and two closed canopy deciduous forest stands (with overstory dominated by tulip poplar) in eastern Maryland. Model-simulated signals were compared with waveforms recorded by the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) over these regions. Model simulations show good agreement with SLICER signals having a slow decay of the waveform. The analysis of the effects of multiple scattering shows that multiply scattered photons magnify the amplitude of the reflected signal, especially that originating from the lower portions of the canopy.
NASA Astrophysics Data System (ADS)
Rodgers, A.; Petersson, A.; Nilsson, S.; Sjogreen, B.; McCandless, K.
2006-12-01
As part of the 1906 San Francisco earthquake centenary, the USGS developed a three-dimensional seismic velocity and attenuation model for Northern California based on detailed geologic and geophysical constraints. The model was used to predict ground motions for the 1906 rupture. In this study we evaluate the model to assess its ability to accurately predict ground motions from moderate earthquakes recorded on broadband stations. Satisfactory prediction of ground motions from these events will provide hope for accurate modeling of future scenario earthquakes. Simulations were performed on large parallel computer(s) with a new elastic finite difference code developed at LLNL. We simulated broadband ground motions (0-0.25 Hz) for several moderate (magnitude 3.5-5.0) earthquakes in the region observed at Berkeley Digital Seismic Network (BDSN) broadband stations. These events are well located and can be modeled with simple point moment tensor sources (taken from the Berkeley Seismological Laboratory catalog), helping to isolate the effects of structure on the waveforms. These data sample the region's diverse tectonic structures, such as the bay muds, sedimentary basins and hard rock complexes. Preliminary results indicate that the simulations reproduce many important features in the data. For example, observed long duration surface waves are often predicted for complex paths (traveling across contrasting structures) and through sedimentary basins. Excellent waveform fits were frequently obtained for long-period comparisons (0.02-0.1) and good fits were often obtained for shorter periods. We will attempt higher frequency simulations to test the ability of the model to match the high frequency response. Finally, we performed large scenario earthquake simulations for the Hayward Fault. These simulations predict large amplifications across the Santa Clara and San Ramon/Livermore Valley sedimentary basins and with the Sacramento/San Joaquin River Delta.
Reference respiratory waveforms by minimum jerk model analysis
Anetai, Yusuke Sumida, Iori; Takahashi, Yutaka; Yagi, Masashi; Mizuno, Hirokazu; Ogawa, Kazuhiko; Ota, Seiichi
2015-09-15
Purpose: CyberKnife{sup ®} robotic surgery system has the ability to deliver radiation to a tumor subject to respiratory movements using Synchrony{sup ®} mode with less than 2 mm tracking accuracy. However, rapid and rough motion tracking causes mechanical tracking errors and puts mechanical stress on the robotic joint, leading to unexpected radiation delivery errors. During clinical treatment, patient respiratory motions are much more complicated, suggesting the need for patient-specific modeling of respiratory motion. The purpose of this study was to propose a novel method that provides a reference respiratory wave to enable smooth tracking for each patient. Methods: The minimum jerk model, which mathematically derives smoothness by means of jerk, or the third derivative of position and the derivative of acceleration with respect to time that is proportional to the time rate of force changed was introduced to model a patient-specific respiratory motion wave to provide smooth motion tracking using CyberKnife{sup ®}. To verify that patient-specific minimum jerk respiratory waves were being tracked smoothly by Synchrony{sup ®} mode, a tracking laser projection from CyberKnife{sup ®} was optically analyzed every 0.1 s using a webcam and a calibrated grid on a motion phantom whose motion was in accordance with three pattern waves (cosine, typical free-breathing, and minimum jerk theoretical wave models) for the clinically relevant superior–inferior directions from six volunteers assessed on the same node of the same isocentric plan. Results: Tracking discrepancy from the center of the grid to the beam projection was evaluated. The minimum jerk theoretical wave reduced the maximum-peak amplitude of radial tracking discrepancy compared with that of the waveforms modeled by cosine and typical free-breathing model by 22% and 35%, respectively, and provided smooth tracking for radial direction. Motion tracking constancy as indicated by radial tracking discrepancy
Waveform Inversion of Synthetic Ocean Models in the Laplace Domain
NASA Astrophysics Data System (ADS)
Rosado, H.; Blacic, T. M.; Jun, H.; Shin, C.
2014-12-01
In seismic oceanography, the processed images show where small temperature changes (as little as 0.03°C) occur, although they do not give absolute temperatures. To get a 2-D temperature map, the data must be inverted for sound speed, which is then converted to temperature using equations of state. Full waveform inversion requires a starting model that is iteratively updated until the residuals converge. Global search algorithms such as Genetic Algorithm do not require a starting model close to the true model, but are computationally exhausting. Local search inversion is less expensive, but requires a reasonably accurate starting model. Unfortunately, most marine seismic data has little associated hydrographic data and so it is difficult to create starting models close enough to the true model for convergence throughout the target area. In addition, the band-limited nature of seismic data makes it inherently challenging to extract the long wavelength sound speed trend directly from seismic data. Laplace domain inversion (LDI) developed by Changsoo Shin and colleagues requires only a rudimentary starting model to produce smooth background sound speed models without requiring prior information about the medium. It works by transforming input data to the Laplace domain, and then examining the zero frequency component of the damped wavefield to extract a smooth sound speed model - basically, removing higher frequency fluctuations to expose background trends. This ability to use frequencies below those effectively propagated by the seismic source is what enables LDI to produce the smooth background trend from the data. We applied LDI to five synthetic data sets based on simplified models of oceanographic features. Using LDI, we were able to recover smoothed versions of our synthetic models, showing the viability of the method for creating sound speed profiles suitable for use as starting models for other methods of inversion that output more detailed models.
NASA Astrophysics Data System (ADS)
Rodgers, Arthur J.; Schwartz, Susan Y.
We report low average crustal P-wave velocities (5.9-6.1 km/s, Poisson's ratio 0.23-0.27, thickness 68-76 km) in southern Tibet from modelling regional Pnl waveforms recorded by the 1991-1992 Tibetan Plateau Experiment. We also find that the mantle lithosphere beneath the Indus-Tsangpo Suture and the Lhasa Terrane is shield-like (Pn velocity 8.20-8.25 km/s, lid thickness 80-140 km, positive velocity gradient 0.0015-0.0025 s-1). Analysis of relative Pn travel time residuals requires a decrease in the mantle velocities beneath the northern Lhasa Terrane, the Banggong-Nujiang Suture and the southern Qiangtang Terrane. Tectonic and petrologic considerations suggest that low bulk crustal velocities could result from a thick (50-60 km) felsic upper crust with vertically limited and laterally pervasive partial melt. These results are consistent with underthrusting of Indian Shield lithosphere beneath the Tibetan Plateau to at least the central Lhasa Terrane.
Waveform tomography of crustal structure in the south San Francisco Bay region
Pollitz, F.F.; Fletcher, J.P.
2005-01-01
We utilize a scattering-based seismic tomography technique to constrain crustal tructure around the southern San Francisco Bay region (SFBR). This technique is based on coupled traveling wave scattering theory, which has usually been applied to the interpretation of surface waves in large regional-scale studies. Using fully three-dimensional kernels, this technique is here applied to observed P, S, and surface waves of intermediate period (3-4 s dominant period) observed following eight selected regional events. We use a total of 73 seismograms recorded by a U.S. Geological Survey short-period seismic array in the western Santa Clara Valley, the Berkeley Digital Seismic Network, and the Northern California Seismic Network. Modifications of observed waveforms due to scattering from crustal structure include (positive or negative) amplification, delay, and generation of coda waves. The derived crustal structure explains many of the observed signals which cannot be explained with a simple layered structure. There is sufficient sensitivity to both deep and shallow crustal structure that even with the few sources employed in the present study, we obtain shallow velocity structure which is reasonably consistent with previous P wave tomography results. We find a depth-dependent lateral velocity contrast across the San Andreas fault (SAF), with higher velocities southwest of the SAF in the shallow crust and higher velocities northeast of the SAF in the midcrust. The method does not have the resolution to identify very slow sediment velocities in the upper approximately 3 km since the tomographic models are smooth at a vertical scale of about 5 km. Copyright 2005 by the American Geophysical Union.
Use and abuse of the model waveform accuracy standards
Lindblom, Lee
2009-09-15
Accuracy standards have been developed to ensure that the waveforms used for gravitational-wave data analysis are good enough to serve their intended purposes. These standards place constraints on certain norms of the frequency-domain representations of the waveform errors. Examples are given here of possible misinterpretations and misapplications of these standards, whose effect could be to vitiate the quality control they were intended to enforce. Suggestions are given for ways to avoid these problems.
Decomposition of LiDAR waveforms by B-spline-based modeling
NASA Astrophysics Data System (ADS)
Shen, Xiang; Li, Qing-Quan; Wu, Guofeng; Zhu, Jiasong
2017-06-01
Waveform decomposition is a widely used technique for extracting echoes from full-waveform LiDAR data. Most previous studies recommended the Gaussian decomposition approach, which employs the Gaussian function in laser pulse modeling. As the Gaussian-shape assumption is not always satisfied for real LiDAR waveforms, some other probability distributions (e.g., the lognormal distribution, the generalized normal distribution, and the Burr distribution) have also been introduced by researchers to fit sharply-peaked and/or heavy-tailed pulses. However, these models cannot be universally used, because they are only suitable for processing the LiDAR waveforms in particular shapes. In this paper, we present a new waveform decomposition algorithm based on the B-spline modeling technique. LiDAR waveforms are not assumed to have a priori shapes but rather are modeled by B-splines, and the shape of a received waveform is treated as the mixture of finite transmitted pulses after translation and scaling transformation. The performance of the new model was tested using two full-waveform data sets acquired by a Riegl LMS-Q680i laser scanner and an Optech Aquarius laser bathymeter, comparing with three classical waveform decomposition approaches: the Gaussian, generalized normal, and lognormal distribution-based models. The experimental results show that the B-spline model performed the best in terms of waveform fitting accuracy, while the generalized normal model yielded the worst performance in the two test data sets. Riegl waveforms have nearly Gaussian pulse shapes and were well fitted by the Gaussian mixture model, while the B-spline-based modeling algorithm produced a slightly better result by further reducing 6.4% of fitting residuals, largely benefiting from alleviating the adverse impact of the ringing effect. The pulse shapes of Optech waveforms, on the other hand, are noticeably right-skewed. The Gaussian modeling results deviated significantly from original signals, and
Seismic waveform inversion best practices: regional, global and exploration test cases
NASA Astrophysics Data System (ADS)
Modrak, Ryan; Tromp, Jeroen
2016-09-01
Reaching the global minimum of a waveform misfit function requires careful choices about the nonlinear optimization, preconditioning and regularization methods underlying an inversion. Because waveform inversion problems are susceptible to erratic convergence associated with strong nonlinearity, one or two test cases are not enough to reliably inform such decisions. We identify best practices, instead, using four seismic near-surface problems, one regional problem and two global problems. To make meaningful quantitative comparisons between methods, we carry out hundreds of inversions, varying one aspect of the implementation at a time. Comparing nonlinear optimization algorithms, we find that limited-memory BFGS provides computational savings over nonlinear conjugate gradient methods in a wide range of test cases. Comparing preconditioners, we show that a new diagonal scaling derived from the adjoint of the forward operator provides better performance than two conventional preconditioning schemes. Comparing regularization strategies, we find that projection, convolution, Tikhonov regularization and total variation regularization are effective in different contexts. Besides questions of one strategy or another, reliability and efficiency in waveform inversion depend on close numerical attention and care. Implementation details involving the line search and restart conditions have a strong effect on computational cost, regardless of the chosen nonlinear optimization algorithm.
Waveform model of a laser altimeter for an elliptical Gaussian beam.
Yue, Ma; Mingwei, Wang; Guoyuan, Li; Xiushan, Lu; Fanlin, Yang
2016-03-10
The current waveform model of a laser altimeter is based on the Gaussian laser beam of the fundamental mode, whose cross section is a circular spot, whereas some of the cross sections of Geoscience Laser Altimeter System lasers are closer to elliptical spots. Based on the expression of the elliptical Gaussian beam and the waveform theory of laser altimeters, the primary parameters of an echo waveform were derived. In order to examine the deduced expressions, a laser altimetry waveform simulator and waveform processing software were programmed and improved under the circumstance of an elliptical Gaussian beam. The result shows that all the biases between the theoretical and simulated waveforms were less than 0.5%, and the derived model of an elliptical spot is universal and can also be used for the conventional circular spot. The shape of the waveforms is influenced by the ellipticity of the laser spot, the target slope, and the "azimuth angle" between the major axis and the slope direction. This article provides the waveform theoretical basis of a laser altimeter under an elliptical Gaussian beam.
NASA Astrophysics Data System (ADS)
Kim, Seongryong; Rhie, Junkee; Kim, Geunyoung
2011-04-01
We propose a full-grid search procedure for broad-band waveform modelling to determine a 1-D crustal velocity model. The velocity model can be more constrained because of the use of broad-band waveforms instead of traveltimes for the crustal phases, although only a small number of event-station pairs were employed. Despite the time-consuming nature of the full-grid search method to search the whole model parameter space, the use of an empirical relationship between the P- and S-wave velocities can significantly reduce computation time. The proposed method was applied to a case in the southern Korean Peninsula. Broad-band waveforms obtained from two inland earthquakes that occurred on 2007 January 20 (Mw 4.6) and 2004 April 26 (Mw 3.6) were used to test the method. The three-layers over half-space crustal velocity model of the P- and S-wave velocities was estimated. Comparisons of waveform fitness between the final model and previously published models demonstrate advancements in the average value of waveform fitness for the inland earthquakes. In addition, 1-D velocity models were determined for three distinct tectonic regions, namely, the Gyonggi Massif, the Okcheon Belt and the Gyeongsang Basin, which are all located inside the study area. A comparison between the three models demonstrates that the crustal thickness of the southern Korean Peninsula increases from NW to SE and that the lower crustal composition of the Okcheon belt differs from that of the other tectonic regions.
Structure of the upper mantle under the EPR from waveform inversion of regional events
Webb; Forsyth
1998-05-22
Waveform inversions of seismograms recorded at the Mantle Electromagnetic and Tomography (MELT) Experiment ocean bottom seismometer array from regional events with paths following the East Pacific Rise (EPR) require that low shear velocities (<3.7 km/s) extend to depths of more than 100 km below the rise axis. Velocities increase with average crustal age along ray paths. The reconciliation of Love and Rayleigh wave data requires that shear flow has aligned melt pockets or olivine crystals, creating an anisotropic uppermost mantle.
NASA Astrophysics Data System (ADS)
Rhie, Junkee; Kim, Seongryong; Woo, Jeong-Ung; Kang, Tae-Seob
2017-04-01
To obtain a high-resolution crustal three-dimensional (3-D) model, we incorporate multiple regional ambient noise datasets in different scales, which consist of 150 accelerometer stations (1-6 s group velocity), 37 regional broadband stations (5-30 s group and phase velocity), and longer period phase velocity maps from previous study (25-40 s phase velocity). A 3-D structure of shear wave velocity is constrained by integrating one-dimensional depth profiles from inversions of surface wave dispersions. The model estimation is carried out thoroughly in a trans-dimensional and hierarchical Bayesian inversion framework, such that the resulting model is less biased by arbitrary assumptions in the inversion process. To obtain P-wave velocity structure, then, a previous estimation of the variation of Vp/Vs ratio is applied. A 1-D velocity model will be replaced by this new 3-D model for determining accurate hypocenters and source processes of local earthquakes in the region. In addition, the new model will make more reliable seismic hazard analysis for scenario earthquakes possible. Before adopting the new model for various applications, it is necessary to validate it. To verify the validity of the model, full-waveform simulations for recent local earthquakes are performed. Four well observed moderate earthquakes in the southern Korean Peninsula are considered for waveform simulations. The comparison between synthetic and observed waveforms shows that the new model reasonably well represents the seismic wave propagation characteristics in the southern Korean Peninsula.
Slinkard, Megan; Heck, Stephen; Schaff, David; Bonal, Nedra; Daily, David; Young, Christopher; Richards, Paul
2016-06-28
Using template waveforms from aftershocks of the Wenchuan earthquake (12 May 2008, M_{s} 8.0) listed in a global bulletin and continuous data from eight regional stations, we detected more than 6000 additional events in the mainshock source region from 1 May to 12 August 2008. These new detections obey Omori’s law, extend the magnitude of completeness downward by 1.1 magnitude units, and lead to a more than fivefold increase in number of known aftershocks compared with the global bulletins published by the International Data Centre and the Inter national Seismological Centre. Moreover, we detected more M > 2 events than were listed by the Sichuan Seismograph Network. Several clusters of these detections were then relocated using the double-difference method, yielding locations that reduced travel-time residuals by a factor of 32 compared with the initial bulletin locations. Finally, our results suggest that using waveform correlation on a few regional stations can find aftershock events very effectively and locate them with precision.
Slinkard, Megan; Heck, Stephen; Schaff, David; ...
2016-06-28
Using template waveforms from aftershocks of the Wenchuan earthquake (12 May 2008, Ms 8.0) listed in a global bulletin and continuous data from eight regional stations, we detected more than 6000 additional events in the mainshock source region from 1 May to 12 August 2008. These new detections obey Omori’s law, extend the magnitude of completeness downward by 1.1 magnitude units, and lead to a more than fivefold increase in number of known aftershocks compared with the global bulletins published by the International Data Centre and the Inter national Seismological Centre. Moreover, we detected more M > 2 events thanmore » were listed by the Sichuan Seismograph Network. Several clusters of these detections were then relocated using the double-difference method, yielding locations that reduced travel-time residuals by a factor of 32 compared with the initial bulletin locations. Finally, our results suggest that using waveform correlation on a few regional stations can find aftershock events very effectively and locate them with precision.« less
Slinkard, Megan; Heck, Stephen; Schaff, David; Bonal, Nedra; Daily, David; Young, Christopher; Richards, Paul
2016-06-28
Using template waveforms from aftershocks of the Wenchuan earthquake (12 May 2008, M_{s} 8.0) listed in a global bulletin and continuous data from eight regional stations, we detected more than 6000 additional events in the mainshock source region from 1 May to 12 August 2008. These new detections obey Omori’s law, extend the magnitude of completeness downward by 1.1 magnitude units, and lead to a more than fivefold increase in number of known aftershocks compared with the global bulletins published by the International Data Centre and the Inter national Seismological Centre. Moreover, we detected more M > 2 events than were listed by the Sichuan Seismograph Network. Several clusters of these detections were then relocated using the double-difference method, yielding locations that reduced travel-time residuals by a factor of 32 compared with the initial bulletin locations. Finally, our results suggest that using waveform correlation on a few regional stations can find aftershock events very effectively and locate them with precision.
NASA Astrophysics Data System (ADS)
Siegel, J. E.; Lizarralde, D.; Dugan, B.; Person, M. A.
2012-12-01
Localized, high-amplitude reflections, overlying a late Pleistocene glacial erosion surface 100 km offshore Massachusetts, USA, have lower compressional wave velocities of up to 200 m/s compared to adjacent sediments of equal depth. This may be the result of lower effective stress from overpressures as high as 1 MPa. To investigate the origin of these low velocity zones, we compare the detailed velocity structure across the high-amplitude regions to adjacent, undisturbed regions through a full waveform inversion, and we forward model the effective stress and overpressure. We relate the full waveform inversion velocities to effective stress with a power-law model. This model predicts effective stresses are 0.6 MPa at 250 m below the sea floor, which equates to an overpressure of 1.0 MPa. To help understand the overpressure source, we model the pressure response to erosion, glacial loading, and sedimentation in 1D. Preliminary models show that late Pleistocene glaciations, including the Last Glacial Maximum (LGM), and rapid sedimentation from glacial lake drainage may be important mechanisms for the generation of the localized regions of high overpressure. Our geophysical observations and interpretations suggest overpressure exists offshore today. Our forward models predict that this overpressure originated during the LGM due to pore pressure generation from rapid loading by glacial ice, however these overpressures are dissipating in the modern, low sedimentation rate environment. These shallow overpressures provide a mechanism to explain the SGD inferred along the Northern Atlantic continental shelf. Our results also provide physical-property observables, specific to location, that can constrain ongoing 3D numerical modeling efforts to deterministically predict the hydrologic history of the continental shelf sediments based on detailed stratigraphic and ice-sheet evolution.
NASA Technical Reports Server (NTRS)
Blair, J. Bryan; Hofton, Michelle A.
1999-01-01
The upcoming generation of laser altimeters record the interaction of emitted laser radiation with terrestrial surfaces in the form of a digitized waveform. We model these laser altimeter return waveforms as the sum of the reflections from individual surfaces within laser footprints, accounting for instrument-specific properties. We compare over 1000 modeled and recorded waveform pairs using the Pearson correlation. We show that we reliably synthesize the vertical structure information for vegetation canopies contained in a medium-large diameter laser footprint from a high-resolution elevation data set.
NASA Astrophysics Data System (ADS)
Louvari, E.; Kiratzi, A.; Papazachos, B.; Hatzidimitriou, P.
- Source parameters for thirteen earthquakes in the SE Adriatic region have been determined using P and SH body-waveform inversion. The results of this modeling are combined with eleven other earthquakes with M>=5 whose focal mechanisms have been determined mainly by waveform modeling. The results confirm that movement on mainly low-angle reverse faults causes the deformation in coastal southern Yugoslavia through Albania up to the Lefkada Island in NW Greece. This zone of thrusting has a NW-SE trend (N34°W), follows the coastline, and dips towards the continent. The slip vectors of these events trend at N229° along the Dalmatian coasts, to N247° along Albania and NW Greece. The deformation is attributed to the continental collision between the Adriatic block to the west and Eurasia to the east. Along the mountain line in eastern Albania (Albanides Mts.) and in NW Greece (Hellenides Mts.), E-W extension is occurring. The E-W extension associated with the orogenic belt could be attributed to a variety of models such as: gravity, internal deformation of the thrust wedge, a probable down bulge of the dense lithosphere of the Adriatic block beneath the Eurasian lithospheric plate in combination with the compressional stresses applied along the collision belt.
NASA Astrophysics Data System (ADS)
Alvarado, Patricia; Ramos, Victor A.
2011-04-01
We investigate the seismic properties of modern crustal seismicity in the northwestern Sierras Pampeanas of the Andean retroarc region of Argentina. We modelled the complete regional seismic broadband waveforms of two crustal earthquakes that occurred in the Sierra de Velasco on 28 May 2002 and in the Sierra de Ambato on 7 September 2004. For each earthquake we obtained the seismic moment tensor inversion (SMTI) and tested for its focal depth. Our results indicate mainly thrust focal mechanism solutions of magnitudes Mw 5.8 and 6.2 and focal depths of 10 and 8 km, respectively. These results represent the larger seismicity and shallower focal depths in the last 100 years in this region. The SMTI 2002 and 2004 solutions are consistent with previous determinations for crustal seismicity in this region that also used seismic waveform modelling. Taken together, the results for crustal seismicity of magnitudes ≥5.0 in the last 30 years are consistent with an average P-axis horizontally oriented by an azimuth of 125° and T-axis orientation of azimuth 241° and plunge 58°. This modern crustal seismicity and the historical earthquakes are associated with two active reverse faulting systems of opposite vergences bounding the eastern margin of the Sierra de Velasco in the south and the southwestern margin of the Sierra de Ambato in the north. Strain recorded by focal mechanisms of the larger seismicity is very consistent over this region and is in good agreement with neotectonic activity during the last 11,000 years by Costa (2008) and Casa et al. (in press); this shows that the dominant deformation in this part of the Sierras Pampeanas is mainly controlled by contraction. Seismic deformation related to propagation of thrusts and long-lived shear zones of this area permit to disregard previous proposals, which suggested an extensional or sinistral regime for the geomorphic evolution since Pleistocene.
NASA Astrophysics Data System (ADS)
Lin, Youzuo; Huang, Lianjie
2017-07-01
Reverse-time migration has the potential to image complex subsurface structures, including steeply-dipping fault zones, but the method requires an accurate velocity model. Acoustic- and elastic-waveform inversion is a promising tool for high-resolution velocity model building. Because of the ill-posedness of acoustic- and elastic-waveform inversion, it is a great challenge to obtain accurate velocity models containing sharp interfaces. To improve velocity model building, we develop an acoustic- and elastic-waveform inversion method with an interface-guided modified total-variation regularization scheme to improve the inversion accuracy and robustness, particularly for models with sharp interfaces and steeply-dipping fault zones with widths much smaller than the seismic wavelength. The new regularization scheme incorporates interface information into seismic full-waveform inversion. The interface information of subsurface interfaces is obtained iteratively using migration imaging during waveform inversion. Seismic migration is robust for subsurface imaging. Our new acoustic- and elastic-waveform inversion takes advantage of the robustness of migration imaging to improve velocity estimation. We use synthetic seismic data for a complex model containing sharp interfaces and several steeply-dipping fault zones to validate the improved capability of our new acoustic- and elastic-waveform inversion method. Our inversion results are much better than those produced without using interface-guided regularization. Acoustic- and elastic-waveform inversion with an interface-guided modified total-variation regularization scheme has the potential to accurately build subsurface velocity models with sharp interfaces and/or steep fault zones.
Connolly, Mark; He, Xing; Gonzalez, Nestor; Vespa, Paul; DiStefano, Joe; Hu, Xiao
2014-01-01
Due to the inaccessibility of the cranial vault, it is difficult to study cerebral blood flow dynamics directly. A mathematical model can be useful to study these dynamics. The model presented here is a novel combination of a one-dimensional fluid flow model representing the major vessels of the circle of Willis (CoW), with six individually parameterized auto-regulatory models of the distal vascular beds. This model has the unique ability to simulate high temporal resolution flow and velocity waveforms, amenable to pulse-waveform analysis, as well as sophisticated phenomena such as auto-regulation. Previous work with human patients has shown that vasodilation induced by CO2 inhalation causes 12 consistent pulse-waveform changes as measured by the Morphological Clustering and Analysis of Intracranial Pressure algorithm. To validate this model, we simulated vasodilation and successfully reproduced 9 out of the 12 pulse-waveform changes. A subsequent sensitivity analysis found that these 12 pulse-waveform changes were most affected by the parameters associated with the shape of the smooth muscle tension response and vessel elasticity, providing insight into the physiological mechanisms responsible for observed changes in the pulse-waveform shape. PMID:24389244
Connolly, Mark; He, Xing; Gonzalez, Nestor; Vespa, Paul; DiStefano, Joe; Hu, Xiao
2014-03-01
Due to the inaccessibility of the cranial vault, it is difficult to study cerebral blood flow dynamics directly. A mathematical model can be useful to study these dynamics. The model presented here is a novel combination of a one-dimensional fluid flow model representing the major vessels of the circle of Willis (CoW), with six individually parameterized auto-regulatory models of the distal vascular beds. This model has the unique ability to simulate high temporal resolution flow and velocity waveforms, amenable to pulse-waveform analysis, as well as sophisticated phenomena such as auto-regulation. Previous work with human patients has shown that vasodilation induced by CO2 inhalation causes 12 consistent pulse-waveform changes as measured by the morphological clustering and analysis of intracranial pressure algorithm. To validate this model, we simulated vasodilation and successfully reproduced 9 out of the 12 pulse-waveform changes. A subsequent sensitivity analysis found that these 12 pulse-waveform changes were most affected by the parameters associated with the shape of the smooth muscle tension response and vessel elasticity, providing insight into the physiological mechanisms responsible for observed changes in the pulse-waveform shape. Copyright © 2013 IPEM. All rights reserved.
NASA Astrophysics Data System (ADS)
Blackman, Jonathan; Field, Scott; Galley, Chad; Hemberger, Daniel; Scheel, Mark; Schmidt, Patricia; Smith, Rory; SXS Collaboration Collaboration
2016-03-01
We are now in the advanced detector era of gravitational wave astronomy, and the merger of two black holes (BHs) is one of the most promising sources of gravitational waves that could be detected on earth. To infer the BH masses and spins, the observed signal must be compared to waveforms predicted by general relativity for millions of binary configurations. Numerical relativity (NR) simulations can produce accurate waveforms, but are prohibitively expensive to use for parameter estimation. Other waveform models are fast enough but may lack accuracy in portions of the parameter space. Numerical relativity surrogate models attempt to rapidly predict the results of a NR code with a small or negligible modeling error, after being trained on a set of input waveforms. Such surrogate models are ideal for parameter estimation, as they are both fast and accurate, and have already been built for the case of non-spinning BHs. Using 250 input waveforms, we build a surrogate model for waveforms from the Spectral Einstein Code (SpEC) for a subspace of precessing systems.
NASA Astrophysics Data System (ADS)
Schaff, D. P.; Kim, W.; Waldhauser, F.; Richards, P. G.
2004-12-01
We are evaluating a method of locating seismic sources (earthquakes, explosions) based on the large-scale use of waveform cross-correlation (WCC) measurements instead of the conventional measurements of seismic wave arrival time (phase picks). WCC measurements have been demonstrated to be 10 to 100 times more accurate, where they can be obtained. The principal issue we are exploring is the extent to which a significant fraction of seismicity can be located using WCC measurements. We are studying the Charlevoix region in eastern Canada, the New Madrid seismic zone in the central United States, and northern California. In the first two regions the datasets have been assembled from scratch working in conjunction with regional network operators. For Charlevoix, courtesy of the Geological Survey of Canada, we now have 2,470 events with corresponding catalog, phase, and waveform data. For New Madrid, two datasets have been acquired. The first is from the PANDA deployment between 1989 and 1992, which consists of 884 events with bulletin and waveform information. The second is from the Center for Earthquake Research and Information (CERI) network, operated by University of Memphis, from which we currently have waveform data for 1995-2003, with extensive catalog and phase data. Preliminary WCC results of the PANDA network indicate that 68% (597 out of 884 events) correlate with cross-correlation coefficients (CC) above 0.7 at four or more stations. Four stations are the minimum required to obtain a location estimate. Both P- and S-waves are correlated on all three components. The window lengths are 1 s and the lags searched over are also 1 s. It appears in a few examples that similar correlations are possible over 1 to 10 kilometer inter-event separation distances due to a site resonance from soft sediments underneath certain stations. In the Charlevoix seismic zone there are only 10% of the events that meet the criteria of CC > 0.7 at four or more stations. To explain this
NASA Astrophysics Data System (ADS)
Qi, Youzheng; Huang, Ling; Wu, Xin; Zhu, Wanhua; Fang, Guangyou; Yu, Gang
2017-07-01
Quantitative modeling of the transient electromagnetic (TEM) response requires consideration of the full transmitter waveform, i.e., not only the specific current waveform in a half cycle but also the bipolar repetition. In this paper, we present a novel temporal interpolation and convolution (TIC) method to facilitate the accurate TEM modeling. We first calculate the temporal basis response on a logarithmic scale using the fast digital-filter-based methods. Then, we introduce a function named hamlogsinc in the framework of discrete signal processing theory to reconstruct the basis function and to make the convolution with the positive half of the waveform. Finally, a superposition procedure is used to take account of the effect of previous bipolar waveforms. Comparisons with the established fast Fourier transform method demonstrate that our TIC method can get the same accuracy with a shorter computing time.
Very long-period GPS waveforms. What can GPS bring to Earth seismic velocity models?
NASA Astrophysics Data System (ADS)
Kelevitz, K.; Houlie, N.; Nissen-Meyer, T.; Boschi, L.; Giardini, D.; Rothacher, M.
2014-12-01
It is now admitted that high rate GPS observations can provide reliable surface displacement waveforms. For long-period (T > 5s) transients, it was shown that GPS and seismometer (STS-1) displacements are in agreement at least for vertical component [Houlié et al., 2011]. We propose here to supplement existing long-period seismic networks with high rate (>= 1Hz) GPS data in order to improve the resolution of global seismic velocity models. We aim at extending the use of GPS measurements beyond the range of STS-1 in the low frequency end (T>1000s). We present the results of the processing of 1Hz GPS records of the Hokkaido, Sumatra and Tohoku earthquakes (25th of September, 2003, Mw = 8.3; 26th of December, 2004, Mw = 8.9; 11th of March, 2011, Mw = 9.1, respectively). 3D waveforms phase time-series have been used to recover the ground motion histories at the GPS sites. Through the better resolution of inversion of the GPS phase observations, we determine displacement waveforms of periods ranging from 30 seconds to 1300 seconds for a selection of sites. We compare inverted GPS waveforms with STS-1 waveforms, superconducting gravity waveforms and synthetic waveforms computed using 3D global wave propagation with SPECFEM. We find that the GPS waveforms are in agreement with the SPECFEM synthetic data and are able to fill the period-gap between the broadband seismometer STS-1 data and the normal mode period range detected by the superconducting gravimeters. References: Houlié, N., G. Occhipinti, T. Blanchard, N. Shapiro, P. Lognonne, and M. Murakami (2011), New approach to detect seismic surface waves in 1Hz-sampled GPS time series, Scientific reports, 1, 44.
NASA Astrophysics Data System (ADS)
Nguyen, Xuan Nhi; Dahm, Torsten; Grevemeyer, Ingo
2009-10-01
The construction of S-wave velocity models of marine sediments down to hundreds of meters below the seafloor is important in a number of disciplines. One of the most significant trends in marine geophysics is to use interface waves to estimate shallow shear velocities which play an important role in determining the shallow crustal structure. In marine settings, the waves trapped near the fluid-solid interface are called Scholte waves, and this is the subject of the study. In 1998, there were experiments on the Ninetyeast Ridge (Central Indian Ocean) to study the shallow seismic structure at the drilled site. The data were acquired by both ocean bottom seismometer and ocean bottom hydrophone. A new type of seafloor implosion sources has been used in this experiment, which successfully excited fast and high frequency (>500 Hz) body waves and slow, intermediate frequency (<20 Hz) Scholte waves. The fundamental and first higher mode Scholte waves have both been excited by the implosion source. Here, the Scholte waves are investigated with a full waveform modeling and a group velocity inversion approach. Shear wave velocities for the uppermost layers of the region are inferred and results from the different methods are compared. We find that the full waveform modeling is important to understand the intrinsic attenuation of the Scholte waves between 1 and 20 Hz. The modeling shows that the S-wave velocity varies from 195 to 350 m/s in the first 16 m of the uppermost layer. Depths levels of high S-wave impedance contrasts compare well to the layer depth derived from a P-wave analysis as well as from drilling data. As expected, the P- to S-wave velocity ratio is very high in the uppermost 16 m of the seafloor and the Poisson ratio is nearly 0.5. Depth levels of high S-wave impedance contrasts are comparable to the layer depth derived from drilling data.
Hamilton, Robert B; Baldwin, Kevin; Vespa, Paul; Bergsneider, Marvin; Hu, Xiao
2012-01-01
The objective of this study is to investigate the relationship between intracranial pressure (ICP) pulse waveform morphology and selected hydrodynamic metrics of cerebrospinal fluid (CSF) movement using a novel method for ICP pulse pressure regional analysis based on the Morphological Clustering and Analysis of Continuous Intracranial Pulse (MOCAIP) algorithm.
NASA Technical Reports Server (NTRS)
Blair, J. Bryan; Hofton, M. A.
1999-01-01
The upcoming generation of operational spaceborne laser altimeters (i.e VCL and GLAS) record the interaction of emitted laser radiation with terrestrial surfaces in the form of a digitized waveform. We show that we can accurately model return laser altimeter waveforms as the sum of the reflections from individual surfaces within laser footprints. In one case, we predict return waveforms using high resolution elevation data generated by a small-footprint laser altimeter in a dense tropical forest. We compare over 3000 modeled and recorded waveform pairs using the Pearson correlation. The modeled and recorded waveforms are highly correlated, with a mean correlation of 0.90 and a median of 0.95. The mean correlation is highly dependent on the relative positions of the data sets. By shifting the relative locations of the two compared data sets, we infer that the data are colocated to within 0.4$\\sim$m horizontally and 0.12$\\sim$m vertically. The high degree of correlation shows that we can reliably synthesize the vertical structure information measured by medium-large footprint laser altimeters for complex, dense vegetation.
NASA Technical Reports Server (NTRS)
Blair, J. Bryan; Hofton, M. A.
1999-01-01
The upcoming generation of operational spaceborne laser altimeters (i.e VCL and GLAS) record the interaction of emitted laser radiation with terrestrial surfaces in the form of a digitized waveform. We show that we can accurately model return laser altimeter waveforms as the sum of the reflections from individual surfaces within laser footprints. In one case, we predict return waveforms using high resolution elevation data generated by a small-footprint laser altimeter in a dense tropical forest. We compare over 3000 modeled and recorded waveform pairs using the Pearson correlation. The modeled and recorded waveforms are highly correlated, with a mean correlation of 0.90 and a median of 0.95. The mean correlation is highly dependent on the relative positions of the data sets. By shifting the relative locations of the two compared data sets, we infer that the data are colocated to within 0.4$\\sim$m horizontally and 0.12$\\sim$m vertically. The high degree of correlation shows that we can reliably synthesize the vertical structure information measured by medium-large footprint laser altimeters for complex, dense vegetation.
NASA Astrophysics Data System (ADS)
Xing, Yanqiu; Qiu, Sai; Ding, Jianhua; Tian, Jing
2016-06-01
Estimation of forest aboveground biomass (AGB) is a critical challenge for understanding the global carbon cycle because it dominates the dynamics of the terrestrial carbon cycle. Light Detection and Ranging (LiDAR) system has a unique capability for estimating accurately forest canopy height, which has a direct relationship and can provide better understanding to the forest AGB. The Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat) is the first polarorbiting LiDAR instrument for global observations of Earth, and it has been widely used for extracting forest AGB with footprints of nominally 70 m in diameter on the earth's surface. However, the GLAS footprints are discrete geographically, and thus it has been restricted to produce the regional full coverage of forest AGB. To overcome the limit of discontinuity, the Hyper Spectral Imager (HSI) of HJ-1A with 115 bands was combined with GLAS waveforms to predict the regional forest AGB in the study. Corresponding with the field investigation in Wangqing of Changbai Mountain, China, the GLAS waveform metrics were derived and employed to establish the AGB model, which was used further for estimating the AGB within GLAS footprints. For HSI imagery, the Minimum Noise Fraction (MNF) method was used to decrease noise and reduce the dimensionality of spectral bands, and consequently the first three of MNF were able to offer almost 98% spectral information and qualified to regress with the GLAS estimated AGB. Afterwards, the support vector regression (SVR) method was employed in the study to establish the relationship between GLAS estimated AGB and three of HSI MNF (i.e. MNF1, MNF2 and MNF3), and accordingly the full covered regional forest AGB map was produced. The results showed that the adj.R2 and RMSE of SVR-AGB models were 0.75 and 4.68 t hm-2 for broadleaf forests, 0.73 and 5.39 t hm-2 for coniferous forests and 0.71 and 6.15 t hm-2 for mixed forests respectively. The
NASA Astrophysics Data System (ADS)
Kitov, Ivan; Bobrov, Dmitry; Rozhkov, Mikhail; Johansson, Peder
2013-04-01
Waveform cross correlation substantially improves detection, phase association, and event building procedures at the International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organization. There were 50% to 100% events extra to the official Reviewed Event Bulletin (REB) were found in the aftershock sequences of small, middle size, and very big earthquakes. Several per cent of the events reported in the REB were not found with cross correlation even when all aftershocks were used as master events. These REB events are scrutinized in interactive analysis in order to reveal the reason of the cross correlation failure. As a corroborative method, we use detailed regional catalogues, which often include aftershocks with magnitudes between 2.0 and 3.0. Since the resolution of regional networks is by at least one unit of magnitude higher, the REB events missed from the relevant regional catalogues are considered as bogus. We compare events by origin time and location because the regional networks and the International Monitoring System are based on different sets of seismic stations and phase comparison is not possible. Three intracontinental sequences have been studied: after the March 20, 2008 earthquake in China (mb(IDC)=5.4), the May 20, 2012 event in Italy (mb(IDC)=5.3), and one earthquake (mb(IDC)=5.6) in Virginia, USA (August 23, 2011). Overall, most of the events not found by cross correlation are missing from the relevant regional catalogues. At the same time, these catalogues confirm most of additional REB events found only by cross correlation. This observation supports all previous findings of the improved quality of events built by cross correlation.
NASA Astrophysics Data System (ADS)
Kodera, Y.; Sakai, S.
2012-12-01
Development of a method of automatic processing of seismic waves is needed since there are limitations to manually picking out earthquake events from seismograms. However, there is no practical method to automatically detect arrival times of P and S waves in seismograms. One typical example of previously proposed methods is automatic detection by using AR model (e.g. Kitagawa et al., 2004). This method seems not to be effective for seismograms contaminated with spike noise, because it cannot distinguish non-stationary signals generated by earthquakes from those generated by noise. The difficulty of distinguishing the signals is caused by the fact that the automatic detection system has a lack of information on time series variation of seismic waves. We expect that an automatic detection system that includes the information on seismic waves is more effective for seismograms contaminated with noise. So we try to adapt Hidden Markov Model (HMM) to construct seismic wave models and establish a new automatic detection method. HMM has been widely used in many fields such as voice recognition (e.g. Bishop, 2006). With the use of HMM, P- or S-waveform models that include envelops can be constructed directly and semi-automatically from lots of observed waveform data of P or S waves. These waveform models are expected to become more robust if the quantity of observation data increases. We have constructed seismic wave models based on HMM from seismograms observed in Ashio, Japan. By using these models, we have tried automatic detection of arrival times of earthquake events in Ashio. Results show that automatic detection based on HMM is more effective for seismograms contaminated with noise than that based on AR model.
Model-Based Analysis and Design of Waveforms for Efficient Neural Stimulation
Grill, Warren M.
2016-01-01
The design space for electrical stimulation of the nervous system is extremely large, and because the response to stimulation is highly non-linear, the selection of stimulation parameters to achieve a desired response is a challenging problem. Computational models of the response of neurons to extracellular stimulation allow analysis of the effects of stimulation parameters on neural excitation and provide an approach to select or design optimal parameters of stimulation. Here, I review the use of computational models to understand the effects of stimulation waveform on the energy efficiency of neural excitation and to design novel stimulation waveforms to increase the efficiency of neural stimulation. PMID:26541380
NASA Astrophysics Data System (ADS)
Smithyman, B.; Clowes, R. M.
2009-12-01
Multichannel vibroseis reflection surveys are prevalent in the land exploration seismic industry because of benefits in speed and cost, along with reduced environmental impact when compared to explosive sources. Since the downgoing energy must travel through the shallow subsurface, an improved model of near-surface velocity can in theory substantially improve the resolution of deeper reflections. We describe techniques aimed at allowing the use of vibroseis data for long-offset refraction processing of first-arrival traveltimes and waveforms. Refraction processing of surface vibroseis data is typically limited to near-offset refraction statics. Velocity models of the shallow subsurface can be built to facilitate CDP stacking and migration, but these models are typically coarse and of limited use for interpretation. Waveform tomography combines inversion of first-arrival traveltime data with full waveform inversion of densely-sampled refracted arrivals. Since inversion of the waveform amplitude and phase is not limited by the ray-theory approximation, identification of low-velocity zones and small scattering targets is possible. Incorporating a wide range of offsets is critical for a more complete characterization of the near-surface. Because of the use of a non-linear frequency-domain approach to the solution of this inverse problem, low data frequencies are important in comparison with conventional reflection processing. Through the use of waveform tomography, we plan to build useful, detailed near-surface velocity models for both the reflection work flow and direct interpretation. Several difficulties exist in first-arrival analysis and waveform inversion of vibroseis data. The mixed-phase vibroseis source signature exhibits variations in phase with offset that are difficult to quantify without detailed a priori knowledge of the near-surface. This causes difficulties with picking and initial model building, which is critical for non-linear waveform inversion. A
Amelard, Robert; Clausi, David A.; Wong, Alexander
2016-01-01
Photoplethysmographic imaging is an optical solution for non-contact cardiovascular monitoring from a distance. This camera-based technology enables physiological monitoring in situations where contact-based devices may be problematic or infeasible, such as ambulatory, sleep, and multi-individual monitoring. However, automatically extracting the blood pulse waveform signal is challenging due to the unknown mixture of relevant (pulsatile) and irrelevant pixels in the scene. Here, we propose a signal fusion framework, FusionPPG, for extracting a blood pulse waveform signal with strong temporal fidelity from a scene without requiring anatomical priors. The extraction problem is posed as a Bayesian least squares fusion problem, and solved using a novel probabilistic pulsatility model that incorporates both physiologically derived spectral and spatial waveform priors to identify pulsatility characteristics in the scene. Evaluation was performed on a 24-participant sample with various ages (9–60 years) and body compositions (fat% 30.0 ± 7.9, muscle% 40.4 ± 5.3, BMI 25.5 ± 5.2 kg·m−2). Experimental results show stronger matching to the ground-truth blood pulse waveform signal compared to the FaceMeanPPG (p < 0.001) and DistancePPG (p < 0.001) methods. Heart rates predicted using FusionPPG correlated strongly with ground truth measurements (r2 = 0.9952). A cardiac arrhythmia was visually identified in FusionPPG’s waveform via temporal analysis. PMID:28018712
Amelard, Robert; Clausi, David A; Wong, Alexander
2016-12-01
Photoplethysmographic imaging is an optical solution for non-contact cardiovascular monitoring from a distance. This camera-based technology enables physiological monitoring in situations where contact-based devices may be problematic or infeasible, such as ambulatory, sleep, and multi-individual monitoring. However, automatically extracting the blood pulse waveform signal is challenging due to the unknown mixture of relevant (pulsatile) and irrelevant pixels in the scene. Here, we propose a signal fusion framework, FusionPPG, for extracting a blood pulse waveform signal with strong temporal fidelity from a scene without requiring anatomical priors. The extraction problem is posed as a Bayesian least squares fusion problem, and solved using a novel probabilistic pulsatility model that incorporates both physiologically derived spectral and spatial waveform priors to identify pulsatility characteristics in the scene. Evaluation was performed on a 24-participant sample with various ages (9-60 years) and body compositions (fat% 30.0 ± 7.9, muscle% 40.4 ± 5.3, BMI 25.5 ± 5.2 kg·m(-2)). Experimental results show stronger matching to the ground-truth blood pulse waveform signal compared to the FaceMeanPPG (p < 0.001) and DistancePPG (p < 0.001) methods. Heart rates predicted using FusionPPG correlated strongly with ground truth measurements (r(2) = 0.9952). A cardiac arrhythmia was visually identified in FusionPPG's waveform via temporal analysis.
Effective-one-body waveforms for binary neutron stars using surrogate models
NASA Astrophysics Data System (ADS)
Lackey, Benjamin D.; Bernuzzi, Sebastiano; Galley, Chad R.; Meidam, Jeroen; Van Den Broeck, Chris
2017-05-01
Gravitational-wave observations of binary neutron star systems can provide information about the masses, spins, and structure of neutron stars. However, this requires accurate and computationally efficient waveform models that take ≲1 s to evaluate for use in Bayesian parameter estimation codes that perform 1 07- 1 08 waveform evaluations. We present a surrogate model of a nonspinning effective-one-body waveform model with ℓ=2 , 3, and 4 tidal multipole moments that reproduces waveforms of binary neutron star numerical simulations up to merger. The surrogate is built from compact sets of effective-one-body waveform amplitude and phase data that each form a reduced basis. We find that 12 amplitude and 7 phase basis elements are sufficient to reconstruct any binary neutron star waveform with a starting frequency of 10 Hz. The surrogate has maximum errors of 3.8% in amplitude (0.04% excluding the last 100 M before merger) and 0.043 rad in phase. This leads to typical mismatches of 10-5-10-4 for Advanced LIGO depending on the component masses, with a worst case match of 7 ×10-4 when both stars have masses ≥2 M⊙. The version implemented in the LIGO Algorithm Library takes ˜0.07 s to evaluate for a starting frequency of 30 Hz and ˜0.8 s for a starting frequency of 10 Hz, resulting in a speed-up factor of O (1 03) relative to the original matlab code. This allows parameter estimation codes to run in days to weeks rather than years, and we demonstrate this with a nested sampling run that recovers the masses and tidal parameters of a simulated binary neutron star system.
Blackman, Jonathan; Field, Scott E; Galley, Chad R; Szilágyi, Béla; Scheel, Mark A; Tiglio, Manuel; Hemberger, Daniel A
2015-09-18
Simulating a binary black hole coalescence by solving Einstein's equations is computationally expensive, requiring days to months of supercomputing time. Using reduced order modeling techniques, we construct an accurate surrogate model, which is evaluated in a millisecond to a second, for numerical relativity (NR) waveforms from nonspinning binary black hole coalescences with mass ratios in [1, 10] and durations corresponding to about 15 orbits before merger. We assess the model's uncertainty and show that our modeling strategy predicts NR waveforms not used for the surrogate's training with errors nearly as small as the numerical error of the NR code. Our model includes all spherical-harmonic _{-2}Y_{ℓm} waveform modes resolved by the NR code up to ℓ=8. We compare our surrogate model to effective one body waveforms from 50M_{⊙} to 300M_{⊙} for advanced LIGO detectors and find that the surrogate is always more faithful (by at least an order of magnitude in most cases).
Constraining the general linear model for sensible hemodynamic response function waveforms.
Ciftçi, Koray; Sankur, Bülent; Kahya, Yasemin P; Akin, Ata
2008-08-01
We propose a method to do constrained parameter estimation and inference from neuroimaging data using general linear model (GLM). Constrained approach precludes unrealistic hemodynamic response function (HRF) estimates to appear at the outcome of the GLM analysis. The permissible ranges of waveform parameters were determined from the study of a repertoire of plausible waveforms. These parameter intervals played the role of prior distributions in the subsequent Bayesian analysis of the GLM, and Gibbs sampling was used to derive posterior distributions. The method was applied to artificial null data and near infrared spectroscopy (NIRS) data. The results show that constraining the GLM eliminates unrealistic HRF waveforms and decreases false activations, without affecting the inference for "realistic" activations, which satisfy the constraints.
Veille, J C; Youngstrom, P; Kanaan, C; Wilson, B
1988-12-01
The umbilical artery waveform was assessed in 18 normal nonlaboring patients before and after full surgical epidural anesthesia for repeat cesarean section. Using range-gated pulsed Doppler ultrasound, we found that the waveform analysis of the umbilical artery close to its placental insertion did not change significantly. These results suggest that no deleterious effect on fetoplacental circulation occurs with this form of anesthesia as long as maternal blood pressure is normal.
NASA Astrophysics Data System (ADS)
Martin, Roland; Chevrot, Sébastien; Wang, Yi; Spangenberg, Hannah; Goubet, Marie; Monteiller, Vadim; Komatitsch, Dimitri; Seoane, Lucia; Dufréchou, Grégory
2017-04-01
We present a hybrid inversion method that allows us to image density distributions at the regional scale using both seismic and gravity data. One main goal is to obtain densities and seismic wave velocities (P and S) in the lithosphere with a fine resolution to get important constraints on the mineralogic composition and thermal state of the lithosphere. In the context of the Pyrenees (located between Spain and France), accurate Vp and Vs seismic velocity models are computed first on a 3D spectral element grid at the scale of the Pyrenees by inverting teleseismic full waveforms. In a second step, Vp velocities are mapped to densities using empirical relations to build an a priori density model. BGI and BRGM Bouguer gravity anomaly data sets are then inverted on the same 3D spectral element grid as the Vp model at a resolution of 1-2 km by using high-order numerical integration formulae. Solutions are compared to those obtained using classical semi-analytical techniques. This procedure opens the possibility to invert both teleseismic and gravity data on the same finite-element grid. It can handle topography of the free surface in the same spectral-element distorted mesh that is used to solve the wave equation, without performing extra interpolations between different grids and models. WGS84 curvature, SRTM or ETOPO1 topographies are used.
NASA Astrophysics Data System (ADS)
Auer, Ludwig; Boschi, Lapo; van Driel, Martin; Becker, Thorsten; Nissen-Meyer, Tarje; Sigloch, Karin; Hosseini-zad, Kasra; Giardini, Domenico
2014-05-01
In a recent study (Auer et al. 2013, in revision) we have devised a novel tomography approach to image radially anisotropic shear-velocity variations in the Earth's mantle. By applying our tomography toolbox to a comprehensive compilation of surface-wave phase delays from fundamental modes up to the 6th overtone and cross-correlation traveltimes of major body-wave phases, we derived the multi-resolution tomography model SAVANI, which is one of the first whole-mantle models of radial S-wave anisotropy. Here we illustrate the first steps towards the second iteration of our model ("SAVANI2"), in which we define Europe and the surrounding regions as the target area for a higher-resolution regional revision of our initial model. To this end, we augment our global database with additional teleseismic and regional broadband measurements recorded within the last five years. We download raw waveforms from the Orfeus and IRIS data centers in a fully automated way with a python based toolbox and extract multiple-frequency traveltime delays in the period range between 5 and 25 s employing the method of Sigloch et al. (2006). Furthermore, we replace the crustal model CRUST2.0 with its successor CRUST1. Importantly, waveform observations will be interpreted using Fréchet sensitivity kernels computed with AxiSEM (Nissen-Meyer et al., 2007), which is an efficient visco-elastic spectral element solver for axisymmetric background models. The main idea behind SAVANI2 is to keep semi-approximate (ray) theory where appropriate (global long-wavelength structure, surface wave dispersion), but to revert to a full-waveform interpretation where necessary (regional scale, non-geometrical wave phenomena). Our hybrid approach to waveform inversion has multi-scale capabilities and is essentially equivalent to the first iteration step of a Gauss-Newton type inverse problem, thus allowing full access to the model resolution matrix. The set of algorithms we are developing represent a
Laplace-domain waveform modeling and inversion for the 3D acoustic-elastic coupled media
NASA Astrophysics Data System (ADS)
Shin, Jungkyun; Shin, Changsoo; Calandra, Henri
2016-06-01
Laplace-domain waveform inversion reconstructs long-wavelength subsurface models by using the zero-frequency component of damped seismic signals. Despite the computational advantages of Laplace-domain waveform inversion over conventional frequency-domain waveform inversion, an acoustic assumption and an iterative matrix solver have been used to invert 3D marine datasets to mitigate the intensive computing cost. In this study, we develop a Laplace-domain waveform modeling and inversion algorithm for 3D acoustic-elastic coupled media by using a parallel sparse direct solver library (MUltifrontal Massively Parallel Solver, MUMPS). We precisely simulate a real marine environment by coupling the 3D acoustic and elastic wave equations with the proper boundary condition at the fluid-solid interface. In addition, we can extract the elastic properties of the Earth below the sea bottom from the recorded acoustic pressure datasets. As a matrix solver, the parallel sparse direct solver is used to factorize the non-symmetric impedance matrix in a distributed memory architecture and rapidly solve the wave field for a number of shots by using the lower and upper matrix factors. Using both synthetic datasets and real datasets obtained by a 3D wide azimuth survey, the long-wavelength component of the P-wave and S-wave velocity models is reconstructed and the proposed modeling and inversion algorithm are verified. A cluster of 80 CPU cores is used for this study.
NASA Astrophysics Data System (ADS)
Tseng, Tai-Lin; Hsu, Hsin-Chih; Jian, Pei-Ru; Huang, Bor-Shouh; Hu, Jyr-Ching; Chung, Sun-Lin
2016-11-01
The continental collision between Arabia and Eurasia created large strike-slip faults in Turkey as well as mountains in the Caucasus and the volcanic plateau between them. In this study, we use regional waveforms of a new seismic array deployed between 2008 and 2012 to constrain the focal mechanisms and depths of small to moderate sized earthquakes occurring in the western part of the Central Caucasus and northeast Turkey. The distribution of aftershocks and the twelve focal mechanisms involved in the sequence of the 2009 earthquake in Racha are clearly a reactivation of a deeper segment of the 1991 M7 Racha rupture zone. The deeper segment is not well connected to the shallower décollement separating the basement and sedimentary basin. The earthquakes we determined in northeastern Turkey and southern Georgia are related to the strike-slip fault system. We further combined all of the reliably determined focal mechanisms over the last 30 years to investigate the current stress status of the crust in three areas: Racha in the western Greater Caucasus, Javakheti near the Lesser Caucasus and in Northeast Turkey. Our results show that the directions of maximum compressional stress consistently fall within - 2 to 14°N throughout the entire study region. This appears to be controlled by the continental collision. Nonetheless, the minimum compression switches from vertical (in the Greater Caucasus) to the east-west direction (in northeastern Turkey), due to the westward extrusion of the Anatolia block, which is driven partly by the Hellenic subduction. The transition of the stress field is close to the Javakheti volcanic plateau in the Lesser Caucasus, where the relative magnitude between the principal stresses appears to be strongly variable.
A New Database of Digitized Regional Seismic Waveforms from Nuclear Explosions in Eurasia
NASA Astrophysics Data System (ADS)
Sokolova, I. N.; Richards, P. G.; Kim, W. Y.; Mikhailova, N. N.
2014-12-01
Seismology is an observational science. Hence, the effort to understand details of seismic signals from underground nuclear explosions requires analysis of waveforms recorded from past nuclear explosions. Of principal interest, are regional signals from explosions too small to be reliably identified via teleseismic recording. But the great majority of stations operated today, even those in networks for nuclear explosion monitoring, have never recorded explosion signals at regional distances, because most stations were installed long after the period when most underground nuclear explosions were conducted; and the few nuclear explosions since the early 1990s were mostly recorded only at teleseismic distances. We have therefore gathered thousands of nuclear explosion regional seismograms from more than 200 analog stations operated in the former Soviet Union. Most of them lie in a region stretching approximately 6000 km East-West and 2000 km North-South and including much of Central Asia. We have digitized them and created a modern digital database, including significant metadata. Much of this work has been done in Kazakhstan. Most of the explosions were underground, but several were conducted in the atmosphere. This presentation will characterize the content and overall quality of the new database for signals from nuclear explosions in Eurasia, which were conducted across substantial ranges of yield and shot-point depth, and under a great variety of different geological conditions. This work complements a 20-year collaborative effort which made the original digital recordings of the Borovoye Geophysical Observatory, Kazakhstan, openly available in a modern format (see http://www.ldeo.columbia.edu/res/pi/Monitoring/Data/). For purposes of characterizing explosive sources, it would be of assistance to have seismogram archives from explosions conducted in all regions including the Pacific, North Africa, and the United States (including the Aleutians). Openly available
Zhuang, Tao; Zhao, Lina; Chang, Faliang; Liu, Changchun; Wei, Shoushui; Li, Qiqiang
2014-01-01
Changes of arterial pressure waveform characteristics have been accepted as risk indicators of cardiovascular diseases. Waveform modelling using Gaussian functions has been used to decompose arterial pressure pulses into different numbers of subwaves and hence quantify waveform characteristics. However, the fitting accuracy and computation efficiency of current modelling approaches need to be improved. This study aimed to develop a novel two-stage particle swarm optimizer (TSPSO) to determine optimal parameters of Gaussian functions. The evaluation was performed on carotid and radial artery pressure waveforms (CAPW and RAPW) which were simultaneously recorded from twenty normal volunteers. The fitting accuracy and calculation efficiency of our TSPSO were compared with three published optimization methods: the Nelder-Mead, the modified PSO (MPSO), and the dynamic multiswarm particle swarm optimizer (DMS-PSO). The results showed that TSPSO achieved the best fitting accuracy with a mean absolute error (MAE) of 1.1% for CAPW and 1.0% for RAPW, in comparison with 4.2% and 4.1% for Nelder-Mead, 2.0% and 1.9% for MPSO, and 1.2% and 1.1% for DMS-PSO. In addition, to achieve target MAE of 2.0%, the computation time of TSPSO was only 1.5 s, which was only 20% and 30% of that for MPSO and DMS-PSO, respectively. PMID:24967415
Barbara Romanowicz; Mark Panning
2005-04-23
Adequate path calibrations are crucial for improving the accuracy of seismic event location and origin time, size, and mechanism, as required for CTBT monitoring. There is considerable information on structure in broadband seismograms that is currently not fully utilized. The limitations have been largely theoretical. the development and application to solid earth problems of powerful numerical techniques, such as the Spectral Element Method (SEM), has opened a new era, and theoretically, it should be possible to compute the complete predicted wavefield accurately without any restrictions on the strength or spatial extent of heterogeneity. This approach requires considerable computational power, which is currently not fully reachable in practice. We propose an approach which relies on a cascade of increasingly accurate theoretical approximations for the computation of the seismic wavefield to develop a model of regional structure for the area of Eurasia located between longitudes of 30 and 150 degrees E, and latitudes of -10 to 60 degrees North. The selected area is particularly suitable for the purpose of this experiment, as it is highly heterogeneous, presenting a challenge for calibration purposes, but it is well surrounded by earthquake sources and, even though they are sparsely distributed, a significant number of high quality broadband digital stations exist, for which data are readily accessible through IRIS (Incorporated Research Institutions for Seismology) and the FDSN (Federation of Digital Seismic Networks). The starting models used will be a combination of a-priori 3D models recently developed for this region, combining various geophysical and seismological data, and a major goal of this study will be to refine these models so as to fit a variety of seismic waveforms and phases.
NASA Astrophysics Data System (ADS)
Brenders, A. J.; Pratt, R. G.
2007-01-01
A comprehensive validation of 2-D, frequency-domain, acoustic wave-equation tomography was undertaken in a `blind test', using third-party, realistic, elastic wave-equation data. The synthetic 2-D, wide-angle seismic data were provided prior to a recent workshop on the methods of controlled source seismology; the true model was not revealed to the authors until after the presentation of our waveform tomography results. The original model was specified on a detailed grid with variable P-wave velocity, S-wave velocity, density and viscoelastic Q-factor structure, designed to simulate a section of continental crust 250 km long and 40 km deep. Synthetic vertical and horizontal component data were available for 51 shot locations (spaced every 5 km), recorded at 2779 receivers (spaced every 90 m), evenly spread along the surface of the model. The data contained energy from 0.2 to 15 Hz. Waveform tomography, a combination of traveltime tomography and 2-D waveform inversion of the early arrivals of the seismic waveforms, was used to recover crustal P-velocity structure from the vertical component data, using data from 51 sources, 1390 receivers and frequencies between 0.8 and 7.0 Hz. The waveform tomography result contained apparent structure at wavelength-scale resolution that was not evident on the traveltime tomography result. The predicted (acoustic) waveforms in the final result matched the original elastic data to a high degree of accuracy. During the workshop, the exact model was revealed; over much of the model the waveform tomography results provided a good correspondence with the true model, from large- to intermediate-(wavelength) scales, with a resolution limit on the order of 1 km. A significant, near-surface low-velocity zone, invisible to traveltime methods, was correctly recovered; the results also provided a high-resolution image of the complex structure of the entire crust, and the depth and nature of the crust-mantle transition. Some inaccuracies were
NASA Astrophysics Data System (ADS)
Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ain, A.; Ajith, P.; Alemic, A.; Allen, B.; Allocca, A.; Amariutei, D.; Andersen, M.; Anderson, R.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barbet, M.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Bauchrowitz, J.; Bauer, Th S.; Behnke, B.; Bejger, M.; Beker, M. G.; Belczynski, C.; Bell, A. S.; Bell, C.; Bergmann, G.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biscans, S.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bloemen, S.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, Sukanta; Bosi, L.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Buchman, S.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burman, R.; Buskulic, D.; Buy, C.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Celerier, C.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C.; Colombini, M.; Cominsky, L.; Constancio, M., Jr.; Conte, A.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corpuz, A.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coughlin, S.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Dal Canton, T.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; Debreczeni, G.; Degallaix, J.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Donath, A.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dossa, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dwyer, S.; Eberle, T.; Edo, T.; Edwards, M.; Effler, A.; Eggenstein, H.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endrőczi, G.; Essick, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fehrmann, H.; Fejer, M. M.; Feldbaum, D.; Feroz, F.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Gaonkar, S.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Gräf, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K.; Gustafson, E. K.; Gustafson, R.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hart, M.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Hooper, S.; Hopkins, P.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.; Jaranowski, P.; Ji, Y.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karlen, J.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Keiser, G. M.; Keitel, D.; Kelley, D. B.; Kells, W.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, C.; Kim, K.; Kim, N.; Kim, N. G.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Koehlenbeck, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kremin, A.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, A.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Kwee, P.; Landry, M.; Lantz, B.; Larson, S.; Lasky, P. D.; Lawrie, C.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C.-H.; Lee, H. K.; Lee, H. M.; Lee, J.; Leonardi, M.; Leong, J. R.; Le Roux, A.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B.; Lewis, J.; Li, T. G. F.; Libbrecht, K.; Libson, A.; Lin, A. C.; Littenberg, T. B.; Litvine, V.; Lockerbie, N. A.; Lockett, V.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Lubinski, M. J.; Lück, H.; Luijten, E.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macarthur, J.; Macdonald, E. P.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magana-Sandoval, F.; Mageswaran, M.; Maglione, C.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Manca, G. M.; Mandel, I.; Mandic, V.; Mangano, V.; Mangini, N.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Martinelli, L.; Martynov, D.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; McLin, K.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Meinders, M.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyers, P.; Miao, H.; Michel, C.; Mikhailov, E. E.; Milano, L.; Milde, S.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Moesta, P.; Mohan, M.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nagy, M. F.; Nanda Kumar, D.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nelemans, G.; Neri, I.; Neri, M.; Newton, G.; Nguyen, T.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Palashov, O.; Palomba, C.; Pan, H.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Paris, H.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Penn, S.; Perreca, A.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poeld, J.; Poggiani, R.; Poteomkin, A.; Powell, J.; Prasad, J.; Premachandra, S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Qin, J.; Quetschke, V.; Quintero, E.; Quiroga, G.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rajalakshmi, G.; Rakhmanov, M.; Ramet, C.; Ramirez, K.; Rapagnani, P.; Raymond, V.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Reid, S.; Reitze, D. H.; Rhoades, E.; Ricci, F.; Riles, K.; Robertson, N. A.; Robinet, F.; Rocchi, A.; Rodruck, M.; Rolland, L.; Rollins, J. G.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J. R.; Sannibale, V.; Santiago-Prieto, I.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R.; Scheuer, J.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Shaddock, D.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Singh, R.; Sintes, A. M.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Son, E. J.; Sorazu, B.; Souradeep, T.; Sperandio, L.; Staley, A.; Stebbins, J.; Steinlechner, J.; Steinlechner, S.; Stephens, B. C.; Steplewski, S.; Stevenson, S.; Stone, R.; Stops, D.; Strain, K. A.; Straniero, N.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; ter Braack, A. P. M.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Tse, M.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Urbanek, K.; Vahlbruch, H.; Vajente, G.; Valdes, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Heijningen, J.; van Veggel, A. A.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Verma, S. S.; Vetrano, F.; Viceré, A.; Vincent-Finley, R.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vyachanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Walker, M.; Wallace, L.; Wang, M.; Wang, X.; Ward, R. L.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Williams, K.; Williams, L.; Williams, R.; Williams, T.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yang, Z.; Yoshida, S.; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, Fan; Zhang, L.; Zhao, C.; Zhu, X. J.; Zucker, M. E.; Zuraw, S.; Zweizig, J.; Boyle, M.; Brügmann, B.; Buchman, L. T.; Campanelli, M.; Chu, T.; Etienne, Z. B.; Hannam, M.; Healy, J.; Hinder, I.; Kidder, L. E.; Laguna, P.; Liu, Y. T.; London, L.; Lousto, C. O.; Lovelace, G.; MacDonald, I.; Marronetti, P.; Mösta, P.; Müller, D.; Mundim, B. C.; Nakano, H.; Paschalidis, V.; Pekowsky, L.; Pollney, D.; Pfeiffer, H. P.; Ponce, M.; Pürrer, M.; Reifenberger, G.; Reisswig, C.; Santamaría, L.; Scheel, M. A.; Shapiro, S. L.; Shoemaker, D.; Sopuerta, C. F.; Sperhake, U.; Szilágyi, B.; Taylor, N. W.; Tichy, W.; Tsatsin, P.; Zlochower, Y.
2014-06-01
The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave (GW) astrophysics communities. The purpose of NINJA is to study the ability to detect GWs emitted from merging binary black holes (BBH) and recover their parameters with next-generation GW observatories. We report here on the results of the second NINJA project, NINJA-2, which employs 60 complete BBH hybrid waveforms consisting of a numerical portion modelling the late inspiral, merger, and ringdown stitched to a post-Newtonian portion modelling the early inspiral. In a ‘blind injection challenge’ similar to that conducted in recent Laser Interferometer Gravitational Wave Observatory (LIGO) and Virgo science runs, we added seven hybrid waveforms to two months of data recoloured to predictions of Advanced LIGO (aLIGO) and Advanced Virgo (AdV) sensitivity curves during their first observing runs. The resulting data was analysed by GW detection algorithms and 6 of the waveforms were recovered with false alarm rates smaller than 1 in a thousand years. Parameter-estimation algorithms were run on each of these waveforms to explore the ability to constrain the masses, component angular momenta and sky position of these waveforms. We find that the strong degeneracy between the mass ratio and the BHs’ angular momenta will make it difficult to precisely estimate these parameters with aLIGO and AdV. We also perform a large-scale Monte Carlo study to assess the ability to recover each of the 60 hybrid waveforms with early aLIGO and AdV sensitivity curves. Our results predict that early aLIGO and AdV will have a volume-weighted average sensitive distance of 300 Mpc (1 Gpc) for 10M⊙ + 10M⊙ (50M⊙ + 50M⊙) BBH coalescences. We demonstrate that neglecting the component angular momenta in the waveform models used in matched-filtering will result in a reduction in sensitivity for systems with large component angular momenta. This
NASA Astrophysics Data System (ADS)
Plicka, Vladimir; Zahradnik, Jiri
2013-04-01
Constructing seismic models of the Earth crust serves two major purposes: (i) helping to understand a geologic structure, and (ii) enabling investigations of earthquakes in terms of their location, centroid-moment-tensors, and/or slip-history on faults. We follow line (ii) where even good 1D models are still important. Should the 1D models be usable in seismic waveform modeling, the natural way is to derive them from full waveforms. We developed and tested a method in which full waveforms of an earthquake recorded in a network of local-to-regional stations are inverted into a 1D crustal model, optimally representing the seismic wave propagation. A single-point source approximation is used. The hypocenter position, origin time and a double-couple focal mechanism are fixed at previously determined values. The forward problem is solved by the Discrete Wavenumber method (Bouchon, 1981; Coutant 1989). The inverse problem is solved by the Neighborhood Algorithm (Sambridge, 1999), providing a suite of the well-fitting velocity models. The misfit function is the L2 norm of the difference between the observed and synthetic seismograms. The performance of the method is illustrated on the largest event (Mw 5.3) of the 2010 Efpalio earthquake sequence, Greece (Sokos et al., 2012). Broad-band data at 8 stations are used, spanning epicentral distances from 13 to 100 km. Several different parametrizations are tested. The most interesting results are obtained in the frequency range of 0.05-0.20 Hz for varying 7 layer thicknesses, their Vp and Vs. The corresponding waveform match (variance reduction VR~0.6) is significantly better than with the previously existing models of the region. It strengthens a chance to study some details of the space-time rupture process of future significant events in the Corinth Gulf. As revealed by the correlation and covariance matrices, the mutual trade-off between the thicknesses and velocities, as well as between Vp and Vs is negligible. The
Simple model of complete precessing black-hole-binary gravitational waveforms.
Hannam, Mark; Schmidt, Patricia; Bohé, Alejandro; Haegel, Leïla; Husa, Sascha; Ohme, Frank; Pratten, Geraint; Pürrer, Michael
2014-10-10
The construction of a model of the gravitational-wave (GW) signal from generic configurations of spinning-black-hole binaries, through inspiral, merger, and ringdown, is one of the most pressing theoretical problems in the buildup to the era of GW astronomy. We present the first such model in the frequency domain, PhenomP, which captures the basic phenomenology of the seven-dimensional parameter space of binary configurations with only three key physical parameters. Two of these (the binary's mass ratio and an effective total spin parallel to the orbital angular momentum, which determines the inspiral rate) define an underlying nonprecessing-binary model. The nonprecessing-binary waveforms are then twisted up with approximate expressions for the precessional motion, which require only one additional physical parameter, an effective precession spin, χ(p). All other parameters (total mass, sky location, orientation and polarization, and initial phase) can be specified trivially. The model is constructed in the frequency domain, which will be essential for efficient GW searches and source measurements. We have tested the model's fidelity for GW applications by comparison against hybrid post-Newtonian-numerical-relativity waveforms at a variety of configurations--although we did not use these numerical simulations in the construction of the model. Our model can be used to develop GW searches, to study the implications for astrophysical measurements, and as a simple conceptual framework to form the basis of generic-binary waveform modeling in the advanced-detector era.
NASA Astrophysics Data System (ADS)
Dai, Guohao; Kaazempur-Mofrad, Mohammad R.; Natarajan, Sripriya; Zhang, Yuzhi; Vaughn, Saran; Blackman, Brett R.; Kamm, Roger D.; García-Cardeña, Guillermo; Gimbrone, Michael A., Jr.
2004-10-01
Atherosclerotic lesion localization to regions of disturbed flow within certain arterial geometries, in humans and experimental animals, suggests an important role for local hemodynamic forces in atherogenesis. To explore how endothelial cells (EC) acquire functional/dysfunctional phenotypes in response to vascular region-specific flow patterns, we have used an in vitro dynamic flow system to accurately reproduce arterial shear stress waveforms on cultured human EC and have examined the effects on EC gene expression by using a high-throughput transcriptional profiling approach. The flow patterns in the carotid artery bifurcations of several normal human subjects were characterized by using 3D flow analysis based on actual vascular geometries and blood flow profiles. Two prototypic arterial waveforms, "athero-prone" and "athero-protective," were defined as representative of the wall shear stresses in two distinct regions of the carotid artery (carotid sinus and distal internal carotid artery) that are typically "susceptible" or "resistant," respectively, to atherosclerotic lesion development. These two waveforms were applied to cultured EC, and cDNA microarrays were used to analyze the differential patterns of EC gene expression. In addition, the differential effects of athero-prone vs. athero-protective waveforms were further characterized on several parameters of EC structure and function, including actin cytoskeletal organization, expression and localization of junctional proteins, activation of the NF-B transcriptional pathway, and expression of proinflammatory cytokines and adhesion molecules. These global gene expression patterns and functional data reveal a distinct phenotypic modulation in response to the wall shear stresses present in atherosclerosis-susceptible vs. atherosclerosis-resistant human arterial geometries.
Crustal structure of the Adirondacks determined from broadband teleseismic waveform modeling
NASA Astrophysics Data System (ADS)
Owens, Thomas J.
1987-06-01
Broadband receiver functions developed from teleseismic P waveforms recorded on the midperiod passband of the Department of Energy's Regional Seismic Test Network station RSNY are analyzed to examine the crustal structure beneath the Adirondack Highlands of upstate New York. Radial receiver functions are inverted in the time domain to determine the vertical shear velocity structure at four distinct back azimuths. Lateral changes in structure are identified by examining azimuthal variations in the vertical structure. Southeast of RSNY, our model consists of a thick crust, including a broad crust-mantle transition. The most prominent structure is a high-velocity zone (shear velocity >4.0 km/s) between 18 and 26 km depth which overlies a lower crust of low average shear velocity (< 3.7 km/s). The extent of the high-velocity zone correlates in depth with a highly reflective zone in Consortium for Continental Reflection Profiling profiles SE of RSNY, while the deep low-velocity zone may be correlated with a broad electrical conductivity anomaly in the Adirondacks. This general structure is also seen SW of RSNY, but is more difficult to document at NW and NE azimuths.
Hamschin, Brandon M; Loughlin, Patrick J
2015-11-01
This work considers the design of optimal, energy-constrained transmit signals for active sensing for the case when the designer has incomplete or uncertain knowledge of the target and/or environment. The mathematical formulation is that of a multi-objective optimization problem, wherein one can incorporate a plurality of potential targets, interference, or clutter models and in doing so take advantage of the wide range of results in the literature related to modeling each. It is shown, via simulation, that when the objective function of the optimization problem is chosen to maximize the minimum (i.e., maxmin) probability of detection among all possible model combinations, the optimal waveforms obtained are advantageous. The advantage results because the maxmin waveforms judiciously allocate energy to spectral regions where each of the target models respond strongly and each of the environmental models affect minimal detection performance degradation. In particular, improved detection performance is shown compared to linear frequency modulated transmit signals and compared to signals designed with the wrong target spectrum assumed. Additionally, it is shown that the maxmin design yields performance comparable to an optimal design matched to the correct target/environmental model. Finally, it is proven that the maxmin problem formulation is convex.
NASA Astrophysics Data System (ADS)
Lebedev, S.; Schaeffer, A. J.; Fullea, J.; Pease, V.
2015-12-01
Thermal structure of the lithosphere is reflected in the values of seismic velocities within it. Our new tomographic models of the crust and upper mantle of the Arctic are constrained by an unprecedentedly large global waveform dataset and provide substantially improved resolution, compared to previous models. The new tomography reveals lateral variations in the temperature and thickness of the lithosphere and defines deep boundaries between tectonic blocks with different lithospheric properties and age. The shape and evolution of the geotherm beneath a tectonic unit depends on both crustal and mantle-lithosphere structure beneath it: the lithospheric thickness and its changes with time (these determine the supply of heat from the deep Earth), the crustal thickness and heat production (the supply of heat from within the crust), and the thickness and thermal conductivity of the sedimentary cover (the insulation). Detailed thermal structure of the basins can be modelled by combining seismic velocities from tomography with data on the crustal structure and heat production, in the framework of computational petrological modelling. The most prominent lateral contrasts across the Arctic are between the cold, thick lithospheres of the cratons (in North America, Greenland and Eurasia) and the warmer, non-cratonic blocks. The lithosphere of the Canada Basin is cold and thick, similar to old oceanic lithosphere elsewhere around the world; its thermal structure offers evidence on its lithospheric age and formation mechanism. At 150-250 km depth, the central Arctic region shows a moderate low-velocity anomaly, cooler than that beneath Iceland and N Atlantic. An extension of N Atlantic low-velocity anomaly into the Arctic through the Fram Strait may indicate an influx of N Atlantic asthenosphere under the currently opening Eurasia Basin.
Spike Sorting by Joint Probabilistic Modeling of Neural Spike Trains and Waveforms
Matthews, Brett A.; Clements, Mark A.
2014-01-01
This paper details a novel probabilistic method for automatic neural spike sorting which uses stochastic point process models of neural spike trains and parameterized action potential waveforms. A novel likelihood model for observed firing times as the aggregation of hidden neural spike trains is derived, as well as an iterative procedure for clustering the data and finding the parameters that maximize the likelihood. The method is executed and evaluated on both a fully labeled semiartificial dataset and a partially labeled real dataset of extracellular electric traces from rat hippocampus. In conditions of relatively high difficulty (i.e., with additive noise and with similar action potential waveform shapes for distinct neurons) the method achieves significant improvements in clustering performance over a baseline waveform-only Gaussian mixture model (GMM) clustering on the semiartificial set (1.98% reduction in error rate) and outperforms both the GMM and a state-of-the-art method on the real dataset (5.04% reduction in false positive + false negative errors). Finally, an empirical study of two free parameters for our method is performed on the semiartificial dataset. PMID:24829568
Aligned spin neutron star-black hole mergers: A gravitational waveform amplitude model
NASA Astrophysics Data System (ADS)
Pannarale, Francesco; Berti, Emanuele; Kyutoku, Koutarou; Lackey, Benjamin D.; Shibata, Masaru
2015-10-01
The gravitational radiation emitted during the merger of a black hole with a neutron star is rather similar to the radiation from the merger of two black holes when the neutron star is not tidally disrupted. When tidal disruption occurs, gravitational waveforms can be broadly classified in two groups, depending on the spatial extent of the disrupted material. Extending previous work by some of us, here we present a phenomenological model for the gravitational waveform amplitude in the frequency domain encompassing the three possible outcomes of the merger: no tidal disruption, and "mild" and "strong" tidal disruption. The model is calibrated to 134 general-relativistic numerical simulations of binaries where the black hole spin is either aligned or antialigned with the orbital angular momentum. All simulations were produced using the SACRA code and piecewise polytropic neutron star equations of state. The present model can be used to determine when black-hole binary waveforms are sufficient for gravitational-wave detection, to extract information on the equation of state from future gravitational-wave observations, to obtain more accurate estimates of black hole-neutron star merger event rates, and to determine the conditions under which these systems are plausible candidates as central engines of gamma-ray bursts and macronovae/kilonovae.
Perception of stochastically undersampled sound waveforms: a model of auditory deafferentation
Lopez-Poveda, Enrique A.; Barrios, Pablo
2013-01-01
Auditory deafferentation, or permanent loss of auditory nerve afferent terminals, occurs after noise overexposure and aging and may accompany many forms of hearing loss. It could cause significant auditory impairment but is undetected by regular clinical tests and so its effects on perception are poorly understood. Here, we hypothesize and test a neural mechanism by which deafferentation could deteriorate perception. The basic idea is that the spike train produced by each auditory afferent resembles a stochastically digitized version of the sound waveform and that the quality of the waveform representation in the whole nerve depends on the number of aggregated spike trains or auditory afferents. We reason that because spikes occur stochastically in time with a higher probability for high- than for low-intensity sounds, more afferents would be required for the nerve to faithfully encode high-frequency or low-intensity waveform features than low-frequency or high-intensity features. Deafferentation would thus degrade the encoding of these features. We further reason that due to the stochastic nature of nerve firing, the degradation would be greater in noise than in quiet. This hypothesis is tested using a vocoder. Sounds were filtered through ten adjacent frequency bands. For the signal in each band, multiple stochastically subsampled copies were obtained to roughly mimic different stochastic representations of that signal conveyed by different auditory afferents innervating a given cochlear region. These copies were then aggregated to obtain an acoustic stimulus. Tone detection and speech identification tests were performed by young, normal-hearing listeners using different numbers of stochastic samplers per frequency band in the vocoder. Results support the hypothesis that stochastic undersampling of the sound waveform, inspired by deafferentation, impairs speech perception in noise more than in quiet, consistent with auditory aging effects. PMID:23882176
NASA Astrophysics Data System (ADS)
Huerta, Eliu; Agarwal, Bhanu; Chua, Alvin; George, Daniel; Haas, Roland; Hinder, Ian; Kumar, Prayush; Moore, Christopher; Pfeiffer, Harald
2017-01-01
We recently constructed an inspiral-merger-ringdown (IMR) waveform model to describe the dynamical evolution of compact binaries on eccentric orbits, and used this model to constrain the eccentricity with which the gravitational wave transients currently detected by LIGO could be effectively recovered with banks of quasi-circular templates. We now present the second generation of this model, which is calibrated using a large catalog of eccentric numerical relativity simulations. We discuss the new features of this model, and show that its enhance accuracy makes it a powerful tool to detect eccentric signals with LIGO.
Vliegen, J H; Stam, C J; Keunen, R W
1998-07-01
The objective of this study is to find out which mathematical model best explains the temporal fluctuations of the axial blood flow velocity waveforms in the basal arteries of the brain. Blood flow velocity time series were sampled by transcranial Doppler (TCD) examination of the middle cerebral arteries in 10 healthy volunteers. A recently developed mathematical test (surrogate data analysis) was used to examine whether the spectral Doppler maximum waveform consistent with some prespecified model (null hypothesis). We tested four different null hypothesis. 1. Uncorrelated white noise. 2. Linearly filtered noise. 3. Linearly filtered noise with a static nonlinear amplitude transformation. 4. Noisy nonlinear limit cycle. All null hypotheses except the last one could be rejected. We conclude that the TCD waveforms are best described as nonlinear limit cycle with some percentage of noise, either dynamical and/or observational, which is uncorrelated from one single oscillation to the next. These results are a strong argument to perform nonlinear analysis in future TCD studies in order to obtain a better understanding of the cerebral hemodynamics.
NASA Astrophysics Data System (ADS)
Wulsin, D. F.; Gupta, J. R.; Mani, R.; Blanco, J. A.; Litt, B.
2011-06-01
Clinical electroencephalography (EEG) records vast amounts of human complex data yet is still reviewed primarily by human readers. Deep belief nets (DBNs) are a relatively new type of multi-layer neural network commonly tested on two-dimensional image data but are rarely applied to times-series data such as EEG. We apply DBNs in a semi-supervised paradigm to model EEG waveforms for classification and anomaly detection. DBN performance was comparable to standard classifiers on our EEG dataset, and classification time was found to be 1.7-103.7 times faster than the other high-performing classifiers. We demonstrate how the unsupervised step of DBN learning produces an autoencoder that can naturally be used in anomaly measurement. We compare the use of raw, unprocessed data—a rarity in automated physiological waveform analysis—with hand-chosen features and find that raw data produce comparable classification and better anomaly measurement performance. These results indicate that DBNs and raw data inputs may be more effective for online automated EEG waveform recognition than other common techniques.
NASA Astrophysics Data System (ADS)
Harry, Ian
2014-03-01
The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave astrophysics communities. The purpose of NINJA is to study the ability to detect gravitational waves emitted from merging binary black holes and recover their parameters with next-generation gravitational-wave observatories. We report here on the results of the second NINJA project, NINJA-2, which employs 60 complete binary black hole hybrid waveforms consisting of a numerical portion modelling the late inspiral, merger, and ringdown stitched to a post-Newtonian portion modelling the early inspiral.
Transition zone structure beneath NE China from 3D waveform modelling: Subduction related plumes
NASA Astrophysics Data System (ADS)
Tang, Y.; Grand, S. P.; Niu, F.
2013-12-01
Seismic tomography is currently used to image deep structure on global and local scales. However, tomography inversions usually underestimate amplitudes and likely cannot resolve narrow slow anomalies in the deep mantle. Careful modelling of waveform distortions has the potential to provide better constraints on small scale anomalies in the mantle. We observed strong waveform distortions from several earthquakes that propagated through a low velocity anomaly in the mantle transition zone beneath the Changbaishan volcanic center, Northeast China. The slow anomaly was recently found by tomography results using the NECESSArray. For each earthquake, there exists a cluster of stations whose S-wave amplitude is substantially higher than the other stations. Also, at the stations near the edges of the cluster, the recorded S waves become more complex, usually featuring two pulses with smaller amplitude. We used the spectral-element method (SPECFEM3D) to construct 3D waveforms using the tomographic model as a starting input model. Synthetic modeling indicated that the observed large amplitude and double arrivals for each cluster can be explained by a strong low velocity anomaly with a diameter of ~200 km surrounded by high velocities in the transition zone. The velocity contrast between the slow anomaly and the surrounding medium is at least 8%, which is double that found in the original tomographic model. The large velocity contrast (8%) cannot be the velocity contrast between the slab and normal transition zone mantle because if this were the case a travel time misfit with observed data to the west would result in. We speculate that the slow anomaly is a manifestation of a return flow upwelling through a slab gap in the mantle transition zone that feeds Changbaishan volcanism. The upwelling mantle is likely hot, and the heat source may come from warm, buoyant sub-lithospheric mantle entrained with the sinking lithosphere that requires an opening to rise.
Jacobs, Jonathan B; Dell'Osso, Louis F
2004-07-27
Attempts to simulate dysfunction within ocular motor system (OMS) models capable of exhibiting known ocular motor behavior have provided valuable insight into the structure of the OMS required for normal visual function. The pendular waveforms of congenital nystagmus (CN) appear to be quite complex, composed of a sustained sinusoidal oscillation punctuated by braking saccades and foveating saccades followed by periods of extended foveation. Previously, we verified that these quick phases are generated by the same mechanism as voluntary saccades. We propose a computer model of the ocular motor system that simulates the responses of individuals with pendular CN (including its variable waveforms) based on the instability exhibited by the normal pursuit subsystem and its interaction with other components of the normal ocular motor control system. Fixation data from subjects with CN using both infrared and magnetic search coil oculography were used as templates for our simulations. Our OMS model simulates data from individuals with CN during fixation and in response to complex stimuli. The use of position and velocity efference copy to suppress oscillopsia is the key element in allowing for normal ocular motor behavior. The model's responses to target steps, pulse-steps, ramps, and step-ramps support the hypothetical explanation for the conditions that result in sustained pendular oscillation and the rules for the corrective saccadic responses that shape this underlying oscillation into the well-known family of pendular CN waveforms: pendular (P), pseudopendular (PP), pendular with foveating saccades (Pfs), and pseudopendular with foveating saccades (PPfs). Position error determined the saccadic amplitudes of foveating saccades, whereas stereotypical braking saccades were not dependent on visual information. Additionally, we propose a structure and method of operation for the fixation subsystem, and use it to prolong the low-velocity intervals immediately following
Hall, Marshall V
2015-08-01
An analytical model has been developed for the pile vibration and consequent sound pressure and particle velocity radiated underwater when an offshore cylindrical pile is struck by a drop hammer. The model, which is based on the coupled equations of motion for axial and radial vibration of a thin cylindrical shell, yields frequency-dependent phase velocity and attenuation of these vibrations. The amplitude of the pulse of axial and radial displacement that travels down a pile following an axial impact is described in terms of the hammer properties. Solutions are obtained for the radiated sound pressure and particle velocity, using Junger and Feit's Transform Formulation of the Pressure Field of Cylindrical Radiators [(Acoustical Society of America, New York, 1993), p. 216]. The model is applied to published data on radiated noise from offshore driving of a steel pile. The modeled pressure waveforms at 12-m horizontal range and at 9 hydrophone depths correlate significantly with the measured waveforms. The modeled pressures of the initial positive peaks (appropriately low-pass filtered) agree with data to within 1 dB. The initial negative peaks however exceed the data by up to 7 dB, and as hydrophone depth increases, the model negative peaks have a maximum at 7 m, whereas the data have a maximum at 9 m.
Numerical relativity waveform surrogate model for generically precessing binary black hole mergers
NASA Astrophysics Data System (ADS)
Blackman, Jonathan; Field, Scott E.; Scheel, Mark A.; Galley, Chad R.; Ott, Christian D.; Boyle, Michael; Kidder, Lawrence E.; Pfeiffer, Harald P.; Szilágyi, Béla
2017-07-01
A generic, noneccentric binary black hole (BBH) system emits gravitational waves (GWs) that are completely described by seven intrinsic parameters: the black hole spin vectors and the ratio of their masses. Simulating a BBH coalescence by solving Einstein's equations numerically is computationally expensive, requiring days to months of computing resources for a single set of parameter values. Since theoretical predictions of the GWs are often needed for many different source parameters, a fast and accurate model is essential. We present the first surrogate model for GWs from the coalescence of BBHs including all seven dimensions of the intrinsic noneccentric parameter space. The surrogate model, which we call NRSur7dq2, is built from the results of 744 numerical relativity simulations. NRSur7dq2 covers spin magnitudes up to 0.8 and mass ratios up to 2, includes all ℓ≤4 modes, begins about 20 orbits before merger, and can be evaluated in ˜50 ms . We find the largest NRSur7dq2 errors to be comparable to the largest errors in the numerical relativity simulations, and more than an order of magnitude smaller than the errors of other waveform models. Our model, and more broadly the methods developed here, will enable studies that were not previously possible when using highly accurate waveforms, such as parameter inference and tests of general relativity with GW observations.
Improved Analysis of GW150914 Using a Fully Spin-Precessing Waveform Model
NASA Technical Reports Server (NTRS)
Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Camp, J. B.;
2016-01-01
This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016).]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom) and an 11-dimensional nonprecessing effective-one-body (EOB) model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing EOBNR). Here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing EOBNR) developed within the EOB formalism. We find good agreement with the parameters estimated previously [Abbott et al. Phys. Rev. Lett. 116, 241102 (2016).], and we quote updated component masses of 35(+5)(-3) solar M; and 30(+3)(-4) solar M; (where errors correspond to 90 symmetric credible intervals). We also present slightly tighter constraints on the dimensionless spin magnitudes of the two black holes, with a primary spin estimate is less than 0.65 and a secondary spin estimate is less than 0.75 at 90% probability. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] estimated the systematic parameter-extraction errors due to waveform-model uncertainty by combining the posterior probability densities of precessing IMRPhenom and nonprecessing EOBNR. Here, we find that the two precessing-spin models are in closer agreement, suggesting that these systematic errors are smaller than previously quoted.
Improved Analysis of GW150914 Using a Fully Spin-Precessing Waveform Model
NASA Astrophysics Data System (ADS)
Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Bejger, M.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, C.; Casentini, J.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; De, S.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devine, R. C.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etienne, Z.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Fauchon-Jones, E.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Fenyvesi, E.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gaebel, S.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Geng, P.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jian, L.; Jiménez-Forteza, F.; Johnson, W. W.; Johnson-McDaniel, N. K.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chi-Woong; Kim, Chunglee; Kim, J.; Kim, K.; Kim, N.; Kim, W.; Kim, Y.-M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kissel, J. S.; Klein, B.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Lewis, J. B.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto, C. O.; Lovelace, G.; Lück, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magaña Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, A.; Miller, B. B.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Nedkova, K.; Nelemans, G.; Nelson, T. J. N.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Setyawati, Y.; Shaddock, D. A.; Shaffer, T.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stevenson, S. P.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tomlinson, C.; Tonelli, M.; Tornasi, Z.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; Vallisneri, M.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van der Sluys, M. V.; van Heijningen, J. V.; Vano-Vinuales, A.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Worden, J.; Wright, J. L.; Wu, D. S.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Boyle, M.; Brügmann, B.; Campanelli, M.; Chu, T.; Clark, M.; Haas, R.; Hemberger, D.; Hinder, I.; Kidder, L. E.; Kinsey, M.; Laguna, P.; Ossokine, S.; Pan, Y.; Röver, C.; Scheel, M.; Szilagyi, B.; Teukolsky, S.; Zlochower, Y.; LIGO Scientific Collaboration; Virgo Collaboration
2016-10-01
This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016).]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom) and an 11-dimensional nonprecessing effective-one-body (EOB) model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing EOBNR). Here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing EOBNR) developed within the EOB formalism. We find good agreement with the parameters estimated previously [Abbott et al. Phys. Rev. Lett. 116, 241102 (2016).], and we quote updated component masses of 35-3+5 M⊙ and 3 0-4+3 M⊙ (where errors correspond to 90% symmetric credible intervals). We also present slightly tighter constraints on the dimensionless spin magnitudes of the two black holes, with a primary spin estimate <0.65 and a secondary spin estimate <0.75 at 90% probability. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] estimated the systematic parameter-extraction errors due to waveform-model uncertainty by combining the posterior probability densities of precessing IMRPhenom and nonprecessing EOBNR. Here, we find that the two precessing-spin models are in closer agreement, suggesting that these systematic errors are smaller than previously quoted.
NASA Astrophysics Data System (ADS)
Pierre, C.
2015-12-01
The Earthscope TA deployment across the continental United-State (US) has reached its eastern part, providing the opportunity for high-resolution 3D seismic velocity imaging of both lithosphere and asthenosphere across the entire north-American continent (NA). Previously (Yuan et al., 2014), we presented a 3D radially anisotropic shear wave (Vs) model of North America (NA) lithospheric mantle based on full waveform tomography, combining teleseismic and regional distance data sampling the NA. Regional wavefield computations were performed numerically, using a regional Spectral Element code (RegSEM, Cupillard et al., 2012), while teleseismic computations were performed approximately, using non-linear asymptotic coupling theory (NACT, Li and Romanowicz, 1995). For both datasets, the inversion was performed iteratively, using a Gauss-Newton scheme, with kernels computed using either NACT or the surface wave, path average approximation (PAVA), depending on the source-station distance. We here present a new radially anisotropic lithospheric/asthenospheric model of Vs for NA based entirely on SEM-based numerical waveforms from an augmented dataset of 155 regional events and 70 teleseismic events. The forward wavefield computations are performed using RegSEM down to 40s, starting from our most recent whole mantle 3D radially anisotropic Vs model (SEMUCB-wm1, French and Romanowicz, 2014). To model teleseismic wavefields within our regional computational domain, we developed a new modeling technique which allows us to replace a distant source by virtual sources at the boundary of the computational domain (Masson et al., 2014). Computing virtual sources requires one global simulation per teleseismic events.We then compare two models obtained: one using NACT/PAVA kernels as in our previous work, and another using hybrid kernels, where the Hessian is computed using NACT/PAVA, but the gradient is computed numerically from the adjoint wavefield, providing more accurate kernels
Etchemendy, Pablo E; Eguia, Manuel C; Mesz, Bruno
2014-03-01
In this work, the overall perceived pitch (principal pitch) of pure tones modulated in frequency with an asymmetric waveform is studied. The dependence of the principal pitch on the degree of asymmetric modulation was obtained from a psychophysical experiment. The modulation waveform consisted of a flat portion of constant frequency and two linear segments forming a peak. Consistent with previous results, significant pitch shifts with respect to the time-averaged geometric mean were observed. The direction of the shifts was always toward the flat portion of the modulation. The results from the psychophysical experiment, along with those obtained from previously reported studies, were compared with the predictions of six models of pitch perception proposed in the literature. Even though no single model was able to predict accurately the perceived pitch for all experiments, there were two models that give robust predictions that are within the range of acceptable tuning of modulated tones for almost all the cases. Both models point to the existence of an underlying "stability sensitive" mechanism for the computation of pitch that gives more weight to the portion of the stimuli where the frequency is changing more slowly.
Synthetic waveform modelling of SS precursors from anisotropic upper-mantle discontinuities
NASA Astrophysics Data System (ADS)
Rychert, Catherine A.; Harmon, Nicholas; Schmerr, Nicholas
2014-03-01
SS precursors are a powerful tool for interrogating upper-mantle discontinuity structure. Some of these discontinuities may be defined fully or partially by a variation in anisotropy with depth. Therefore, a careful evaluation of SS precursor waveform predictions from anisotropic discontinuities is required. Here, we perform synthetic waveform modelling to evaluate the potential for using SS precursors to constrain anisotropic discontinuities. We investigate SS precursor amplitudes from models with azimuthally anisotropic discontinuities with assumed hexagonal symmetry. We demonstrate that SS precursor polarity variations are robust across a wide range of earthquake source polarizations for our anisotropic models. While polarity variations are not unique among all potential two-layer models with anisotropic discontinuities, other observables, such as the relative arrival time of the precursor and tectonic settings, may be used to constrain anisotropic structure. We discuss implications for previous imaging of upper-mantle discontinuities that may be anisotropic, such as the Lehmann discontinuity, and discontinuities in depth range of the lithosphere-asthenosphere boundary beneath the Pacific.
NASA Astrophysics Data System (ADS)
Tsuboi, S.; Miyoshi, T.; Nakamura, T.; Obayashi, M.; Tono, Y.
2013-12-01
May 24, 2013 Sea of Okhotsk earthquake (Mw 8.3, depth 640km NEIC) is not only one of the largest events in this general region but also one of the largest deep earthquakes ever recorded. We apply the waveform inversion technique (Kikuchi & Kanamori, 1991) to obtain slip distribution in the source fault of this earthquake in the same manner as our previous work (Nakamura et al., 2010). We use 57 broadband seismograms of IRIS GSN seismic stations with epicentral distance between 30 and 90 degrees. The broadband original data are integrated into ground displacement and band-pass filtered in the frequency band 0.002-1 Hz. Assuming 1D velocity model and the fault size of 135 x 135 km (along strike and dip, respectively), we obtain source rupture model for both nodal planes with high dip angle (81 degree) and low dip angle (10 degree). In order to determine which source rupture model would explain the observations, we calculate broadband synthetic seismograms with these source models for a realistic 3D Earth model using the spectral-element method (Komatitsch & Tromp, 2001). We performed the simulations on 24,576 processors in 3072 nodes of the K-computer in RIKEN. We use a mesh with 200 million spectral-elements, for a total of 13 billion global integration grid points. This translates into an approximate grid spacing of 2.0 km along the Earth's surface. On this number of nodes, a simulation of 50 minutes of wave propagation accurate at periods of 4.5 seconds and longer requires about 5 hours of CPU time. The comparison of the synthetic waveforms with the observation shows that the source rupture model with the low dip angle fault plane better explains the observation especially at stations, which locate south of the epicenter. Our results indicate that the source rupture of this deep earthquake occurred along the horizontal fault plane inside the subducting pacific plate.
NASA Astrophysics Data System (ADS)
Satake, Kenji; Nishimura, Yuichi; Putra, Purna Sulastya; Gusman, Aditya Riadi; Sunendar, Haris; Fujii, Yushiro; Tanioka, Yuichiro; Latief, Hamzah; Yulianto, Eko
2013-09-01
The 2010 Mentawai earthquake (magnitude 7.7) generated a destructive tsunami that caused more than 500 casualties in the Mentawai Islands, west of Sumatra, Indonesia. Seismological analyses indicate that this earthquake was an unusual "tsunami earthquake," which produces much larger tsunamis than expected from the seismic magnitude. We carried out a field survey to measure tsunami heights and inundation distances, an inversion of tsunami waveforms to estimate the slip distribution on the fault, and inundation modeling to compare the measured and simulated tsunami heights. The measured tsunami heights at eight locations on the west coasts of North and South Pagai Island ranged from 2.5 to 9.3 m, but were mostly in the 4-7 m range. At three villages, the tsunami inundation extended more than 300 m. Interviews of local residents indicated that the earthquake ground shaking was less intense than during previous large earthquakes and did not cause any damage. Inversion of tsunami waveforms recorded at nine coastal tide gauges, a nearby GPS buoy, and a DART station indicated a large slip (maximum 6.1 m) on a shallower part of the fault near the trench axis, a distribution similar to other tsunami earthquakes. The total seismic moment estimated from tsunami waveform inversion was 1.0 × 1021 Nm, which corresponded to Mw 7.9. Computed coastal tsunami heights from this tsunami source model using linear equations are similar to the measured tsunami heights. The inundation heights computed by using detailed bathymetry and topography data and nonlinear equations including inundation were smaller than the measured ones. This may have been partly due to the limited resolution and accuracy of publically available bathymetry and topography data. One-dimensional run-up computations using our surveyed topography profiles showed that the computed heights were roughly similar to the measured ones.
Nonspinning black hole-neutron star mergers: A model for the amplitude of gravitational waveforms
NASA Astrophysics Data System (ADS)
Pannarale, Francesco; Berti, Emanuele; Kyutoku, Koutarou; Shibata, Masaru
2013-10-01
Black hole-neutron star binary mergers display a much richer phenomenology than black hole-black hole mergers, even in the relatively simple case—considered in this paper—in which both the black hole and the neutron star are nonspinning. When the neutron star is tidally disrupted, the gravitational wave emission is radically different from the black hole-black hole case and it can be broadly classified in two groups, depending on the spatial extent of the disrupted material. We present a phenomenological model for the gravitational waveform amplitude in the frequency domain that encompasses the three possible outcomes of the merger: no tidal disruption, “mild,” and “strong” tidal disruption. The model is calibrated to general relativistic numerical simulations using piecewise polytropic neutron star equations of state. It should prove useful to extract information on the nuclear equation of state from future gravitational-wave observations, and also to obtain more accurate estimates of black hole-neutron star merger event rates in second- and third-generation interferometric gravitational-wave detectors. We plan to extend and improve the model as longer and more accurate gravitational waveforms become available, and we will make it publicly available online as a Mathematica package. We also present in the Appendix analytical fits of the projected KAGRA noise spectral density, which should be useful in data analysis applications.
Gomberg, J.S.; Masters, T. Guy
1988-01-01
We have developed algorithms for modelling seismic waveforms to constrain regional Earth structure. The seismogram is represented as a sum of locked-mode travelling waves in a layered medium. This representation is convenient as it allows us to model structures with slowly varying heterogeneity and to construct differential seismograms. Describes the techniques we have implemented that enable us to compute synthetic and differential seismograms in an efficient and stable manner. The computational methods are sufficiently rapid that many modes can be included and in some cases the entire seismogram may be modified. These algorithms are applied to model a set of seismograms of southern Mexican earthquakes recorded in northern Mexico. The frequency bandwidth of these data is centred at 0.067 Hz and we demonstrate that even at these relatively high frequencies, many features of the seismogram can be successfully modelled. Our results suggest that the structure within the recording array in northern Mexico is resolvably different from that to the south. We find that the average shear velocity of the lower lithosphere of southern Mexico is very low, approximately 4.3 km s-1. If the low-velocity region is confined to the Trans Mexican Volcanic Belt, the shear velocities between 20-80 km depth are approximately 3.3 km s-1. This may be correlated with partial melt and is consistent with the active volcanism and high heat flow found in the region. -Authors
Propagation of Impulse-Like Waveforms Through the Ionosphere Modeled by Cold Plasma
NASA Astrophysics Data System (ADS)
Giri, D. V.; Dvorak, S. L.
In this chapter, we have studied the propagation of short, impulse-like pulses propagating through the ionosphere. The ionosphere is modeled by simple, cold plasma. The impulse response of such a plasma model is known to consist of two terms. The first term is the impulse itself and the second term contains a Bessel function of first order. This means that the impulse propagates as an impulse followed by a long, oscillatory tail. The numerical example studied here is that of the prototype impulse radiating antenna (IRA). Closed-form expressions are developed for the prototype IRA waveform propagation through the cold-plasma model of the ionosphere. The results are cross-checked with numerical evaluation via a convolution process that uses the known impulse response.
Waveform prediction with travel time model LLNL-G3D assessed by Spectral-Element simulation
NASA Astrophysics Data System (ADS)
Morency, C.; Simmons, N. A.; Myers, S. C.; Johannesson, G.; Matzel, E.
2013-12-01
Seismic monitoring requires accurate prediction of travel times, amplitudes, and whole waveforms. As a first step towards developing a model that is suited to seismic monitoring, LLNL developed the LLNL-G3D P-wave travel time model (Simmons et al., 2012, JGR) to improve seismic event location accuracy. LLNL-G3D fulfills the need to predict travel times from events occurring anywhere in the globe to stations ranging from local to teleseismic distances. Prediction over this distance range requires explicit inclusion of detailed 3-dimensional structure from Earths surface to the core. An open question is how well a model optimized to fit P-wave travel time data can predict waveforms? We begin to address this question by using the P-wave velocities in LLNL-G3D as a proxy for S-wave velocity and density, then performing waveform simulations via the SPECFEM3D_GLOBE spectral-element code. We assess the ability of LLNL-G3D to predict waveforms and draw comparisons to other 3D models available in SPECFEM3D_GLOBE package and widely used in the scientific community. Although we do not expect the P-wave model to perform as well as waveform based models, we view our effort as a first step towards accurate prediction of time times, amplitudes and full waveforms based on a single model. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
NASA Astrophysics Data System (ADS)
Afanasiev, M.; Boehm, C.; van Driel, M.; Krischer, L.; May, D.; Rietmann, M.; Fichtner, A.
2016-12-01
Recent years have been witness to the application of waveform inversion to new and exciting domains, ranging from non-destructive testing to global seismology. Often, each new application brings with it novel wave propagation physics, spatial and temporal discretizations, and models of variable complexity. Adapting existing software to these novel applications often requires a significant investment of time, and acts as a barrier to progress. To combat these problems we introduce Salvus, a software package designed to solve large-scale full-waveform inverse problems, with a focus on both flexibility and performance. Based on a high order finite (spectral) element discretization, we have built Salvus to work on unstructured quad/hex meshes in both 2 or 3 dimensions, with support for P1-P3 bases on triangles and tetrahedra. A diverse (and expanding) collection of wave propagation physics are supported (i.e. coupled solid-fluid). With a focus on the inverse problem, functionality is provided to ease integration with internal and external optimization libraries. Additionally, a python-based meshing package is included to simplify the generation and manipulation of regional to global scale Earth models (quad/hex), with interfaces available to external mesh generators for complex engineering-scale applications (quad/hex/tri/tet). Finally, to ensure that the code remains accurate and maintainable, we build upon software libraries such as PETSc and Eigen, and follow modern software design and testing protocols. Salvus bridges the gap between research and production codes with a design based on C++ mixins and Python wrappers that separates the physical equations from the numerical core. This allows domain scientists to add new equations using a high-level interface, without having to worry about optimized implementation details. Our goal in this presentation is to introduce the code, show several examples across the scales, and discuss some of the extensible design points.
Probabilistic terrain models from waveform airborne LiDAR: AutoProbaDTM project results
NASA Astrophysics Data System (ADS)
Jalobeanu, A.; Goncalves, G. R.
2012-12-01
The main objective of the AutoProbaDTM project was to develop new methods for automated probabilistic topographic map production using the latest LiDAR scanners. It included algorithmic development, implementation and validation over a 200 km2 test area in continental Portugal, representing roughly 100 GB of raw data and half a billion waveforms. We aimed to generate digital terrain models automatically, including ground topography as well as uncertainty maps, using Bayesian inference for model estimation and error propagation, and approaches based on image processing. Here we are presenting the results of the completed project (methodological developments and processing results from the test dataset). In June 2011, the test data were acquired in central Portugal, over an area of geomorphological and ecological interest, using a Riegl LMS-Q680i sensor. We managed to survey 70% of the test area at a satisfactory sampling rate, the angular spacing matching the laser beam divergence and the ground spacing nearly equal to the footprint (almost 4 pts/m2 for a 50cm footprint at 1500 m AGL). This is crucial for a correct processing as aliasing artifacts are significantly reduced. A reverse engineering had to be done as the data were delivered in a proprietary binary format, so we were able to read the waveforms and the essential parameters. A robust waveform processing method has been implemented and tested, georeferencing and geometric computations have been coded. Fast gridding and interpolation techniques have been developed. Validation is nearly completed, as well as geometric calibration, IMU error correction, full error propagation and large-scale DEM reconstruction. A probabilistic processing software package has been implemented and code optimization is in progress. This package includes new boresight calibration procedures, robust peak extraction modules, DEM gridding and interpolation methods, and means to visualize the produced uncertain surfaces (topography
Silvestri, Salvatore; Ladde, Jay G; Brown, James F; Roa, Jesus V; Hunter, Christopher; Ralls, George A; Papa, Linda
2017-06-01
Waveform capnography is considered the gold standard for verification of proper endotracheal tube placement, but current guidelines caution that it is unreliable in low-perfusion states such as cardiac arrest. Recent case reports found that long-deceased cadavers can produce capnographic waveforms. The purpose of this study was to determine the predictive value of waveform capnography for endotracheal tube placement verification and detection of misplacement using a cadaveric experimental model. We conducted a controlled experiment with two intubated cadavers. Tubes were placed within the trachea, esophagus, and hypopharynx utilizing video laryngoscopy. We recorded observations of capnographic waveforms and quantitative end-tidal carbon dioxide (ETCO2) values during tracheal versus extratracheal (i.e., esophageal and hypopharyngeal) ventilations. 106 and 89 tracheal ventilations delivered to cadavers one and two, respectively (n=195) all produced characteristic alveolar waveforms (positive) with ETCO2 values ranging 2-113mmHg. 42 esophageal ventilations (36 to cadaver one and 6 to cadaver two), and 6 hypopharyngeal ventilations (4 to cadaver one and 2 to cadaver two) all resulted in non-alveolar waveforms (negative) with ETCO2 values of 0mmHg. Esophageal and hypopharyngeal measurements were categorized as extratracheal (n=48). A binary classification test showed no false negatives or false positives, indicating 100% sensitivity (NPV 1.0, 95%CI 0.98-1.00) and 100% specificity (PPV 1.0, 95%CI 0.93-1.00). Though current guidelines question the reliability of waveform capnography for verifying endotracheal tube location during low-perfusion states such as cardiac arrest, our findings suggest that it is highly sensitive and specific. Copyright © 2017 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Lui, Semechah K. Y.; Helmberger, Don; Wei, Shengji; Huang, Yihe; Graves, Robert W.
2015-12-01
Results from the 2011 Mw 9.1 Tohoku-Oki megathrust earthquake display a complex rupture pattern, with most of the high-frequency energy radiated from the downdip edge of the seismogenic zone and very little from the large shallow rupture. Current seismic results of smaller earthquakes in this region are confusing due to disagreements among event catalogs on both the event locations (>30 km horizontally) and mechanisms. Here we present an in-depth study of a series of intraslab earthquakes that occurred in a localized region near the downdip edge of the main shock. We explore the validity of 1D velocity model and refine earthquake source parameters for selected key events by performing broadband waveform modeling combining regional networks. These refined source parameters are then used to calibrate paths and further simulate secondary source properties, such as rupture directivity and fault dimension. Calculation of stress changes caused by the main event indicate that the region where these intraslab events occurred are prone to thrust events. This group of intraslab earthquakes suggest the reactivation of a subducted normal fault, and are potentially useful in enhancing our understanding on the downdip shear zone and large outer-rise events.
NASA Astrophysics Data System (ADS)
Dziewonski, A. M.; Chou, T.-A.; Woodhouse, J. H.
1981-04-01
It is possible to use the waveform data not only to derive the source mechanism of an earthquake but also to establish the hypocentral coordinates of the `best point source' (the centroid of the stress glut density) at a given frequency. Thus two classical problems of seismology are combined into a single procedure. Given an estimate of the origin time, epicentral coordinates and depth, an initial moment tensor is derived using one of the variations of the method described in detail by Gilbert and Dziewonski (1975). This set of parameters represents the starting values for an iterative procedure in which perturbations to the elements of the moment tensor are found simultaneously with changes in the hypocentral parameters. In general, the method is stable, and convergence rapid. Although the approach is a general one, we present it here in the context of the analysis of long-period body wave data recorded by the instruments of the SRO and ASRO digital network. It appears that the upper magnitude limit of earthquakes that can be processed using this particular approach is between 7.5 and 8.0; the lower limit is, at this time, approximately 5.5, but it could be extended by broadening the passband of the analysis to include energy with periods shorter that 45 s. As there are hundreds of earthquakes each year with magnitudes exceeding 5.5, the seismic source mechanism can now be studied in detail not only for major events but also, for example, for aftershock series. We have investigated the foreshock and several aftershocks of the Sumba earthquake of August 19, 1977; the results show temporal variation of the stress regime in the fault area of the main shock. An area some 150 km to the northwest of the epicenter of the main event became seismically active 49 days later. The sense of the strike-slip mechanism of these events is consistent with the relaxation of the compressive stress in the plate north of the Java trench. Another geophysically interesting result of our
NASA Astrophysics Data System (ADS)
Wenger, Trey V.; Kepley, Amanda K.; Balser, Dana S.
2017-07-01
HII Region Models fits HII region models to observed radio recombination line and radio continuum data. The algorithm includes the calculations of departure coefficients to correct for non-LTE effects. HII Region Models has been used to model star formation in the nucleus of IC 342.
2007-11-02
This paper was trying to find out a suitable hydraulic model for studying the frequency characteristics between blood pressure waveforms and systemic...were used as organs. We used two kinds of tubes to test the hydraulic model and tried to find out suitable material to stimulate the aorta and its
Bouwmeester, J Christopher; Belenkie, Israel; Shrive, Nigel G; Tyberg, John V
2014-09-01
Conventional haemodynamic analysis of pulmonary venous and left atrial (LA) pressure waveforms yields substantial forward and backward waves throughout the cardiac cycle; the reservoir wave model provides an alternative analysis with minimal waves during diastole. Pressure and flow in a single pulmonary vein (PV) and the main pulmonary artery (PA) were measured in anaesthetized dogs and the effects of hypoxia and nitric oxide, volume loading, and positive-end expiratory pressure (PEEP) were observed. The reservoir wave model was used to determine the reservoir contribution to PV pressure and flow. Subtracting reservoir pressure and flow resulted in 'excess' quantities which were treated as wave-related.Wave intensity analysis of excess pressure and flow quantified the contributions of waves originating upstream (from the PA) and downstream (from the LA and/or left ventricle (LV)).Major features of the characteristic PV waveform are caused by sequential LA and LV contraction and relaxation creating backward compression (i.e.pressure-increasing) waves followed by decompression (i.e. pressure-decreasing) waves. Mitral valve opening is linked to a backwards decompression wave (i.e. diastolic suction). During late systole and early diastole, forward waves originating in the PA are significant. These waves were attenuated less with volume loading and delayed with PEEP. The reservoir wave model shows that the forward and backward waves are negligible during LV diastasis and that the changes in pressure and flow can be accounted for by the discharge of upstream reservoirs. In sharp contrast, conventional analysis posits forward and backward waves such that much of the energy of the forward wave is opposed by the backward wave.
Bouwmeester, J Christopher; Belenkie, Israel; Shrive, Nigel G; Tyberg, John V
2014-01-01
Conventional haemodynamic analysis of pulmonary venous and left atrial (LA) pressure waveforms yields substantial forward and backward waves throughout the cardiac cycle; the reservoir wave model provides an alternative analysis with minimal waves during diastole. Pressure and flow in a single pulmonary vein (PV) and the main pulmonary artery (PA) were measured in anaesthetized dogs and the effects of hypoxia and nitric oxide, volume loading, and positive-end expiratory pressure (PEEP) were observed. The reservoir wave model was used to determine the reservoir contribution to PV pressure and flow. Subtracting reservoir pressure and flow resulted in ‘excess’ quantities which were treated as wave-related. Wave intensity analysis of excess pressure and flow quantified the contributions of waves originating upstream (from the PA) and downstream (from the LA and/or left ventricle (LV)). Major features of the characteristic PV waveform are caused by sequential LA and LV contraction and relaxation creating backward compression (i.e. pressure-increasing) waves followed by decompression (i.e. pressure-decreasing) waves. Mitral valve opening is linked to a backwards decompression wave (i.e. diastolic suction). During late systole and early diastole, forward waves originating in the PA are significant. These waves were attenuated less with volume loading and delayed with PEEP. The reservoir wave model shows that the forward and backward waves are negligible during LV diastasis and that the changes in pressure and flow can be accounted for by the discharge of upstream reservoirs. In sharp contrast, conventional analysis posits forward and backward waves such that much of the energy of the forward wave is opposed by the backward wave. PMID:25015922
NASA Astrophysics Data System (ADS)
Mégnin, Charles; Romanowicz, Barbara
1999-08-01
Most global tomographic models to date are derived using a combination of surface wave (or normal-mode) data and body wave traveltime data. The traveltime approach limits the number of phases available for inversion by requiring them to be isolated on the seismogram. This may ultimately result in limiting the resolution of 3-D structure, at least in some depth ranges in the mantle. In a previous study, we successfully derived a degree 12 whole-mantle SH-velocity tomographic model (SAW12D) using exclusively waveform data. In that inversion, a normal-mode formalism suitable for body waveforms, the non-linear asymptotic coupling theory (NACT), was combined with a body wave windowing scheme, referred to as the `individual wavepacket' (IW) technique, which allows one to assign individual weights to different body wave energy packets. We here compare the relative merits of this choice of theoretical formalism and windowing scheme at different depth ranges in the mantle. Choosing as the reference a model obtained using 7500 transverse-component body wave and 8000 surface wave seismograms and the NACT and IW approaches, we discuss the relative performance of the path average approximation (PAVA), a zeroth-order theoretical approximation appropriate for single-mode surface waves, relative to NACT, and compare the IW windowing scheme with a more standard `full window' (FW) approach, in which a single time window is considered from the first body wave arrival to the fundamental-mode surface waves. The combination PAVA/FW is often used in global tomography to supplement the traveltime data. We show that although the quality of the image derived under the PAVA/FW formalism is very similar to that derived under NACT/IW in the first 300 km of the upper mantle, where the resolution is dominated by surface waves, it deteriorates at greater depths. Images of the lower mantle are shown to be strongly sensitive to the theoretical formalism. In contrast, the resolution of structure
Mellema, Matthew S
2013-08-01
Ventilator waveforms are graphic representations of changes in pressure, flow, and volume within a ventilator circuit. The changes in these parameters over time may be displayed individually (scalars) or plotted one against another (pressure-volume and flow-volume loops). There are 6 basic shapes of scalar waveforms, but only 3 are functionally distinct (square, ramp, and sine). The pressure scalar is a particularly valuable tool when constant flow (e.g., volume control) modes are employed and an inspiratory pause is added. In this setting, inspection of the pressure waveform can allow determination of static, quasistatic, and dynamic compliance, as well as relative changes in airway resistance. Inspection of the pressure waveform can also help to identify many important aspects of patient drug responses, dyssynchrony, and air trapping (auto positive end-expiratory pressure [auto-PEEP]). Depending on the ventilation mode employed, the shape of the flow waveform may be set by the ventilator operator or may be dependent on patient effort and lung mechanics. Decelerating flow patterns have several important advantages when this option is available. Inspection of flow waveforms is crucial in the recognition of dyssynchrony, setting optimal inspiratory times, evaluating responses to bronchodilators, and the recognition of auto-PEEP. The volume waveform often contains somewhat less useful information than the other 2 scalars, but plays a crucial role in the identification of leaks in the circuit. Pressure-volume loops are particularly useful in setting PEEP and peak inspiratory pressure ranges. Inspection of these loops also often helps in the evaluation of lung mechanics, in the identification of circuit leaks, and in the assessment of patient triggering effort. Flow-volume loops are extremely useful in the identification of leaks and excessive airway secretions as well as alterations in airway resistance. Lastly, serial waveform inspection is crucial to the
Idealized digital models for conical reed instruments, with focus on the internal pressure waveform.
Kergomard, J; Guillemain, P; Silva, F; Karkar, S
2016-02-01
Two models for the generation of self-oscillations of reed conical woodwinds are presented. The models use the fewest parameters (of either the resonator or the exciter), whose influence can be quickly explored. The formulation extends iterated maps obtained for lossless cylindrical pipes without reed dynamics. It uses spherical wave variables in idealized resonators, with one parameter more than for cylinders: the missing length of the cone. The mouthpiece volume equals that of the missing part of the cone, and is implemented as either a cylindrical pipe (first model) or a lumped element (second model). Only the first model adds a length parameter for the mouthpiece and leads to the solving of an implicit equation. For the second model, any shape of nonlinear characteristic can be directly considered. The complex characteristic impedance for spherical waves requires sampling times smaller than a round trip in the resonator. The convergence of the two models is shown when the length of the cylindrical mouthpiece tends to zero. The waveform is in semi-quantitative agreement with experiment. It is concluded that the oscillations of the positive episode of the mouthpiece pressure are related to the length of the missing part, not to the reed dynamics.
Chen, Yu; Gao, Kai; Huang, Lianjie; Sabin, Andrew
2016-03-31
Accurate imaging and characterization of fracture zones is crucial for geothermal energy exploration. Aligned fractures within fracture zones behave as anisotropic media for seismic-wave propagation. The anisotropic properties in fracture zones introduce extra difficulties for seismic imaging and waveform inversion. We have recently developed a new anisotropic elastic-waveform inversion method using a modified total-variation regularization scheme and a wave-energy-base preconditioning technique. Our new inversion method uses the parameterization of elasticity constants to describe anisotropic media, and hence it can properly handle arbitrary anisotropy. We apply our new inversion method to a seismic velocity model along a 2D-line seismic data acquired at Eleven-Mile Canyon located at the Southern Dixie Valley in Nevada for geothermal energy exploration. Our inversion results show that anisotropic elastic-waveform inversion has potential to reconstruct subsurface anisotropic elastic parameters for imaging and characterization of fracture zones.
Direct Waveform Inversion: a New Recursive Scheme
NASA Astrophysics Data System (ADS)
Zheng, Y.
2015-12-01
The goal of the full-waveform inversion (FWI) is to find an Earth's model such that the synthetic waveforms computed using the model fit the observed ones. In practice, such a model is found in the context of the perturbation approach in an iterative fashion. Specifically, to find such a model, one starts from an initial global velocity model and perform model updating iteratively based on the Frechet derivative or single scattering by adjoint methods to minimize some cost function. However, this process often leads to local minima for the nonlinear cost function in the optimization and slow or no convergence when the starting model is far from the true model. To solve for the initial-model dependence and the convergence issue, we show a new direct waveform inversion (DWI) idea to directly invert the waveform data recursively by explicitly enforcing the causality principle. The DWI offers the advantage of assuming no global initial model and no iteration is needed for the model updating. Starting from the source-receiver region, the DWI builds the model outward recursively by fitting the earliest part of the reflection waveforms and the DWI process is always convergent. The DWI combines seismic imaging and velocity model building into one single process and this is in contrast to many industrial applications where seismic imaging/migration and velocity modeling building are done alternatively. The DWI idea is applicable to one-, two-, and three-dimensional spaces. We show numerical examples to support our idea using full waveform data including both free-surface and inter-bed multiples. Using reflection seismic data, we show that the DWI can invert for both velocity and density, separately.
On the influence of model parametrization in elastic full waveform tomography
NASA Astrophysics Data System (ADS)
Köhn, D.; De Nil, D.; Kurzmann, A.; Przebindowska, A.; Bohlen, T.
2012-10-01
Elastic Full Waveform Tomography (FWT) aims to reduce the misfit between recorded and modelled data, to deduce a very detailed model of elastic material parameters in the underground. The choice of the elastic model parameters to be inverted affects the convergence and quality of the reconstructed subsurface model. Using the Cross-Triangle-Squares (CTS) model three elastic parametrizations, Lamé parameters m1 = [λ, μ, ρ], seismic velocities m2 = [Vp, Vs, ρ] and seismic impedances m3 = [Ip, Is, ρ] for far-offset reflection seismic acquisition geometries with explosive point sources and free-surface condition are studied. In each CTS model the three elastic parameters are assigned to three different geometrical objects that are spatially separated. The results of the CTS model study reveal a strong requirement of a sequential frequency inversion from low to high frequencies to reconstruct the density model. Using only high-frequency data, cross-talk artefacts have an influence on the quantitative reconstruction of the material parameters, while for a sequential frequency inversion only structural artefacts, representing the boundaries of different model parameters, are present. During the inversion, the Lamé parameters, seismic velocities and impedances could be reconstructed well. However, using the Lamé parametrization ?-artefacts are present in the λ model, while similar artefacts are suppressed when using seismic velocities or impedances. The density inversion shows the largest ambiguity for all parametrizations. However, the artefacts are again more dominant, when using the Lamé parameters and suppressed for seismic velocity and impedance parametrization. The afore mentioned results are confirmed for a geologically more realistic modified Marmousi-II model. Using a conventional streamer acquisition geometry the P-velocity, S-velocity and density models of the subsurface were reconstructed successfully and are compared with the results of the Lam
Full-Waveform Validation of a 3D Seismic Model for Western US
NASA Astrophysics Data System (ADS)
Maceira, M.; Larmat, C. S.; Ammon, C. J.; Chai, C.; Herrmann, R. B.
2014-12-01
Since the initiation of tomographic studies in the 1970s, geoscientists have advanced the art of inferring 3D variations in the subsurface using collections of geophysical (primarily seismic) observables recorded at or near Earth's surface. Advances have come from improvement and enhancement of the available data and from research on theoretical and computational improvements to tomographic and generalized inverse methods. In the last decade, utilizing dense array datasets, these efforts have led to unprecedented 3D images of the subsurface. Understandably, less effort has been expended on model validation to provide an absolute assessment of model uncertainty. Generally models constructed with different data sets and independent computational codes are assessed with geological reasonability and compared other models to gain confidence. The question of "How good is a particular 3D geophysical model at representing the Earth's true nature?" remains largely unaddressed at a time when 3D Earth models are used for both societal and energy security. In the last few years, opportunities have arisen in earth-structure imaging, including the advent of new methods in computational seismology and statistical sciences. We use the unique and extensive High Performance Computing resources available at Los Alamos National Laboratory to explore approaches to realistic model validation. We present results from a study focused on validating a 3D model for the western United States generated using a joint inversion simultaneously fitting interpolated teleseismic P-wave receiver functions, Rayleigh-wave group-velocity estimates between 7 and 250 s period, and high-wavenumber filtered Bouguer gravity observations. Validation of the obtained model is performed through systematic comparison of observed and predicted seismograms generated using the Spectral Element Method, which is a direct numerical solution for full waveform modeling in 3D models, with accuracy of spectral methods.
Advanced Waveform Simulation for Seismic Monitoring
2008-09-01
velocity model. The method separates the main arrivals of the regional waveform into 5 windows: Pnl (vertical and radial components), Rayleigh (vertical and...ranges out to 10°, including extensive observations of crustal thinning and thickening and various Pnl complexities. Broadband modeling in 1D, 2D...existing models perform in predicting the various regional phases, Rayleigh waves, Love waves, and Pnl waves. Previous events from this Basin-and-Range
Sung, Chang Kyu; Han, Bong Soo; Kim, Seung Hyup
2016-01-01
The goal of this study was to evaluate the effect of vascular compliance, resistance, and pulse rate on the resistive index (RI) by using an electrical circuit model to simulate renal blood flow. In order to analyze the renal arterial Doppler waveform, we modeled the renal blood-flow circuit with an equivalent simple electrical circuit containing resistance, inductance, and capacitance. The relationships among the impedance, resistance, and compliance of the circuit were derived from well-known equations, including Kirchhoff's current law for alternating current circuits. Simulated velocity-time profiles for pulsatile flow were generated using Mathematica (Wolfram Research) and the influence of resistance, compliance, and pulse rate on waveforms and the RI was evaluated. Resistance and compliance were found to alter the waveforms independently. The impedance of the circuit increased with increasing proximal compliance, proximal resistance, and distal resistance. The impedance decreased with increasing distal compliance. The RI of the circuit decreased with increasing proximal compliance and resistance. The RI increased with increasing distal compliance and resistance. No positive correlation between impedance and the RI was found. Pulse rate was found to be an extrinsic factor that also influenced the RI. This simulation study using an electrical circuit model led to a better understanding of the renal arterial Doppler waveform and the RI, which may be useful for interpreting Doppler findings in various clinical settings.
NASA Astrophysics Data System (ADS)
Gupta, N.; Callaghan, S.; Graves, R.; Mehta, G.; Zhao, L.; Deelman, E.; Jordan, T. H.; Kesselman, C.; Okaya, D.; Cui, Y.; Field, E.; Gupta, V.; Vahi, K.; Maechling, P. J.
2006-12-01
Researchers from the SCEC Community Modeling Environment (SCEC/CME) project are utilizing the CyberShake computational platform and a distributed high performance computing environment that includes USC High Performance Computer Center and the NSF TeraGrid facilities to calculate physics-based probabilistic seismic hazard curves for several sites in the Southern California area. Traditionally, probabilistic seismic hazard analysis (PSHA) is conducted using intensity measure relationships based on empirical attenuation relationships. However, a more physics-based approach using waveform modeling could lead to significant improvements in seismic hazard analysis. Members of the SCEC/CME Project have integrated leading-edge PSHA software tools, SCEC-developed geophysical models, validated anelastic wave modeling software, and state-of-the-art computational technologies on the TeraGrid to calculate probabilistic seismic hazard curves using 3D waveform-based modeling. The CyberShake calculations for a single probablistic seismic hazard curve require tens of thousands of CPU hours and multiple terabytes of disk storage. The CyberShake workflows are run on high performance computing systems including multiple TeraGrid sites (currently SDSC and NCSA), and the USC Center for High Performance Computing and Communications. To manage the extensive job scheduling and data requirements, CyberShake utilizes a grid-based scientific workflow system based on the Virtual Data System (VDS), the Pegasus meta-scheduler system, and the Globus toolkit. Probabilistic seismic hazard curves for spectral acceleration at 3.0 seconds have been produced for eleven sites in the Southern California region, including rock and basin sites. At low ground motion levels, there is little difference between the CyberShake and attenuation relationship curves. At higher ground motion (lower probability) levels, the curves are similar for some sites (downtown LA, I-5/SR-14 interchange) but different for
NASA Astrophysics Data System (ADS)
Schuberth, B.; Piazzoni, A.; Igel, H.; Bunge, H.; Steinle-Neumann, G.
2006-12-01
For solving inverse problems, forward modeling is needed to obtain predictions for a current set of model parameters. The sophisticated numerical full waveform modeling tools, which are available for several years now, are still not fully applicable to seismological inversions. Thus, the question remains of how we can make use of such tools to learn more about the structure, physics and composition of the Earth. We demonstrate an approach to obtain earth-like seismograms from pure forward modeling. 3D global wave propagation is simulated for a geodynamically derived mantle model (mantle circulation modeling, Bunge et al. 2002). Temperatures from the geodynamic modeling are converted to seismic velocities using a thermodynamically self-consistent mineral physics approach. Assuming a certain mantle composition (e.g. pyrolite) our mineralogic modeling algorithm computes the stable phases at each depth (i.e. pressure) and temperature by system Gibbs free energy minimization. Through the same equations of state (EOS) that model the Gibbs free energy of phases, we compute elastic moduli and density. For this we built a mineral physics database based on calorimetric experiments (enthalpy and entropy of formation, heat capacity) and equation of state parameters. The purpose of this approach is to obtain seismic velocity models independently from seismological observations but based on physical grounds. The resulting seismograms are therefore "physically plausible" and can be compared directly to real data. In this way, one can test various hypothesis about the deep mantle. Additionally, this approach may provide a means to identify new observables of the wave field which are sensitive to geodynamical or physical parameters.
Ikuma, Takeshi; Kunduk, Melda; McWhorter, Andrew J
2012-09-01
High-speed videoendoscopy (HSV) enables the observation and measurement of vibratory behaviors of vocal folds by capturing the laryngeal imagery at high frame rates. The frame rates of commercially available HSVs, however, are still limited to carry out sample-based time-domain objective analyses. To mitigate the resulting lack of temporal resolution, existing studies have employed sum-of-harmonics parametric models to evaluate temporal vocal-fold behaviors. This paper focuses on the other weakness of HSV: its inherent susceptibility to temporal aliasing. Aliasing occurs when there are substantial harmonics above the Nyquist frequency of the HSV camera, and video cameras offer very little means to filter out these harmonics. Although the aliasing effect in HSV data minimally affects many of the laryngeal objective parameter measurements, some parameters, such as harmonics-to-noise ratio and derivative-based parameters, are sensitive to the aliased content. The use of a parametric model with a careful selection of the number of harmonics enables classification of the aliased harmonics as a part of the harmonic signal. Glottal area waveform examples are included to illustrate the modeling capability for cases of normal and disordered vocal folds.
NASA Astrophysics Data System (ADS)
Stark, C. P.; Ekstrom, G.; Hibert, C.; Allen, J.
2011-12-01
Each year, a half-dozen or more kilometer-scale landslides strike mountain regions around the world. Each involves the acceleration and deceleration of millions of tons of debris at bulk rates of 1-3m/s^2, generating peak bulk-averaged forces well in excess of 10GN and exciting seismic waves whose long-period components are detectable at distances exceeding 1000km. We have studied around 40 such teleseismogenic (but not earthquake-triggered) landslides for the period 1980-2013, focusing mainly on inverting the long-period waveforms to infer time-series of landslide dynamical properties (the landslide force history or LFH; [1]), and recently extending our analysis to consider high-frequency seismicity recorded for well-instrumented events. It is now feasible to detect, measure and roughly geolocate >50GN, Msw>4.7 landslide events within a few hours of their occurrence, even if the landslides strike in very remote areas. Each rapid LFH inversion generates a good estimate of the runout geometry, which, for remote events, turns out to be very useful when trying to confirm and precisely locate the landslide occurrence in satellite imagery. With the advent of Landsat 8 it is now feasible to make such a confirmation within a week or so, weather permitting. A recent example is the rapid detection of a ~40Mt landslide in the Wrangell Mountains of Alaska that struck on 2013-07-25: the event was detected and roughly located with a few hours; within a few days, an LFH inversion gave its scale and runout path; the inversion and correlative short-period waveform analysis generated a sharper estimate for its location; a Landsat 8 image over the area was acquired within 8 days, and the new landslide scar was spotted shortly thereafter. This event extends our catalog of landslide source inversions and corroborates our general conclusions from this work, which are: (i) the glaciated mountains of Alaska, notably the St Elias Range and its neighbors, are the most catastrophic
An automated local and regional seismic event location method based on waveform stacking
NASA Astrophysics Data System (ADS)
Grigoli, F.; Cesca, S.; Dahm, T.
2013-12-01
Seismic event location using automated procedures is a very important task in microseismic monitoring as well as within early warning applications. Increasingly large datasets recorded by dense network has recently favoured the development of different automated location methods. These methods are requested to be noise robust, since microseismic records are often characterized by a low signal-to-noise ratios. Most of the aforementioned standard automated location routines rely on automated phase picking and seismic phases identification (generally only P and S) and are generally based on the minimization of the residuals between the theoretical and observed arrival times of the main seismic phases. While different developed approaches allow to accurately pick P onsets, the automatic picking of the S onsets is still challenging, and posing a significant limit to the location performance. We present here a picking free location method based on the use of different characteristic functions, able to identify P and S phases. Both characteristic functions are based on the Short-Term-Average/Long-Term-Average (STA/LTA) traces. For P phases, we use as characteristic function the STA/LTA trace of the vertical energy function, whereas for the S phases we use the STA/LTA traces of a function obtained using the Principal Component Analysis (PCA) technique. In order to locate a seismic event, the space of possible locations is scanned and both P and S characteristic functions are stacked along travel time surfaces corresponding to the selected hypocenter. Iterating this procedure on a three-dimensional grid we retrieve a multidimensional matrix whose absolute maximum corresponds tot he coordinates of the seismic event. We show the performance of our method with different applications, at different scales: 1) s set of low magnitude events recorded by a local network in southern Italy and 2) a set of seismic events recorded by a regional seismic network in Turkey. This work has
NASA Astrophysics Data System (ADS)
Ma, Hongchao; Zhou, Weiwei; Zhang, Liang; Wang, Suyuan
2017-04-01
Full waveform airborne Light Detection And Ranging(LiDAR) data contains abundant information which may overcome some deficiencies of discrete LiDAR point cloud data provided by conventional LiDAR systems. Processing full waveform data to extract more information than coordinate values alone is of great significance for potential applications. The Levenberg-Marquardt (LM) algorithm is a traditional method used to estimate parameters of a Gaussian model when Gaussian decomposition of full waveform LiDAR data is performed. This paper employs the generalized Gaussian mixture function to fit a waveform, and proposes using the grouping LM algorithm to optimize the parameters of the function. It is shown that the grouping LM algorithm overcomes the common drawbacks which arise from the conventional LM for parameter optimization, such as the final results being influenced by the initial parameters, possible algorithm interruption caused by non-numerical elements that occurred in the Jacobian matrix, etc. The precision of the point cloud generated by the grouping LM is evaluated by comparing it with those provided by the LiDAR system and those generated by the conventional LM. Results from both simulation and real data show that the proposed algorithm can generate a higher-quality point cloud, in terms of point density and precision, and can extract other information, such as echo location, pulse width, etc., more precisely as well.
NASA Astrophysics Data System (ADS)
Heinonen, S.; Heinonen, M.; Koivisto, E.
2012-04-01
Reflection seismic data acquired in hard-rock terrains are often difficult to interpret due to complex geological architecture of the target areas. Even fairly simple geological structures, such as folds, can be difficult to identify from the seismic profiles because the reflection method is only able to image the sub-horizontal fold hinges, and no reflections arise from the steep fold limbs. Furthermore, typically acquisition lines in the hard-rock areas are crooked, and the data can rarely be acquired perpendicular to the strikes of the structures, if the strikes are even known. These further complicate the interpretation, because conventional processing techniques fail to compensate for the associated distortions in the ray paths. Full waveform seismic forward modeling can be used to facilitate the interpretations, to help to find optimal processing algorithms for specific structures, and also to guide the planning of a seismic survey. Recent increases in computational power and development of softwares make full wavefield forward modeling possible also for more complex, realistic geological models. In this study, we use Sofi3D-software for seismic forward modeling of 2D reflection seismic data acquired along a crooked acquisition line over a 3D fold structure. The model presents the structures previously interpreted in the Pyhäsalmi VHMS deposit, central Finland. Density, P and S-wave velocities required for the modeling are derived from in-situ drill hole logging data from the Pyhäsalmi mining camp, and Paradigm GoCad is used to build the geological 3D models. Meaningful modeling results require a sufficiently dense modeling grid, however, increasing the grid density comes at the cost of increased running time of the Sofi3D. Thus, careful parameter selection needs to be done before running the forward modeling. The results of the forward modeling aim to facilitate the interpretation of the 2D reflection seismic data available from Pyhäsalmi mining camp. The
Al Hatib, F; Trendafilova, E; Daskalov, I
2000-02-01
The transthoracic electrical impedance is an important defibrillation parameter, affecting the defibrillating current amplitude and energy, and therefore the defibrillation efficiency. A close relationship between transthoracic impedance and defibrillation success rate was observed. Pre-shock measurements (using low amplitude high frequency current) of the impedance were considered a solution for selection of adequate shock voltages or for current-based defibrillation dosage. A recent approach, called 'impedance-compensating defibrillation' was implemented, where the pulse duration was controlled with respect to the impedance measured during the initial phase of the shock. These considerations raised our interest in reassessment of the transthoracic impedance characteristics and the corresponding measurement methods. The purpose of this work is to study the variations of the transthoracic impedance by a continuous measurement technique during the defibrillation shock and comparing the data with results obtained by modelling. Voltage and current impulse waveforms were acquired during cardioversion of patients with atrial fibrillation or flutter. The same type of defibrillation pulse was taken from dogs after induction of fibrillation. The electrodes were located in the anterior position, for both the patients and animals.
Anisotropic Elastic-Waveform Modeling for Fracture Characterization in EGS Reservoirs
Gao, Kai; Huang, Lianjie
2015-01-28
Enhanced geothermal systems (EGS) contain newly created fractures in addition to possible existing fractures. Accurate characterization and monitoring of EGS reservoirs are crucial for optimal placement of new wells and effective extraction of geothermal heat. The fractured reservoirs behave as anisotropic media where seismic waves propagate with different velocities along different directions. In addition, the anisotropic properties of fluid-filled fracture zones could be different from those of dry fracture zones. We develop an optimized rotated staggered-grid elastic-wave finite-difference method for simulating seismic-wave propagation in heterogeneous, anisotropic media. Our new method uses a few extra grid points and optimized finite-difference coefficients based on the space-time dispersion relation, and reduce numerical dispersion of the conventional rotated staggered-grid finite-difference scheme. We validate our new method using synthetic vertical-seismic-profiling (VSP) data for an anisotropic geophysical model built with geologic features found at the Raft River EGS reservoir. This improved and optimized rotated staggered-grid finite-difference method provides an essential tool for analyzing VSP data, reverse-time migration, and elastic-waveform inversion in anisotropic, fractured reservoirs.
Shallow low-velocity zone of the San Jacinto fault from local earthquake waveform modelling
NASA Astrophysics Data System (ADS)
Yang, Hongfeng; Zhu, Lupei
2010-10-01
We developed a method to determine the depth extent of low-velocity zone (LVZ) associated with a fault zone (FZ) using S-wave precursors from local earthquakes. The precursors are diffracted S waves around the edges of LVZ and their relative amplitudes to the direct S waves are sensitive to the LVZ depth. We applied the method to data recorded by three temporary arrays across three branches of the San Jacinto FZ. The FZ dip was constrained by differential traveltimes of P waves between stations at two side of the FZ. Other FZ parameters (width and velocity contrast) were determined by modelling waveforms of direct and FZ-reflected P and S waves. We found that the LVZ of the Buck Ridge fault branch has a width of ~150 m with a 30-40 per cent reduction in Vp and a 50-60 per cent reduction in Vs. The fault dips 70 +/- 5° to southwest and its LVZ extends only to 2 +/- 1 km in depth. The LVZ of the Clark Valley fault branch has a width of ~200 m with 40 per cent reduction in Vp and 50 per cent reduction in Vs. The Coyote Creek branch is nearly vertical and has a LVZ of ~150 m in width and of 25 per cent reduction in Vp and 50 per cent reduction in Vs. The LVZs of these three branches are not centred at the surface fault trace but are located to their northeast, indicating asymmetric damage during earthquakes.
Effects of Forest Disturbances on Forest Structural Parameters Retrieval from Lidar Waveform Data
NASA Technical Reports Server (NTRS)
Ranson, K, Lon; Sun, G.
2011-01-01
The effect of forest disturbance on the lidar waveform and the forest biomass estimation was demonstrated by model simulation. The results show that the correlation between stand biomass and the lidar waveform indices changes when the stand spatial structure changes due to disturbances rather than the natural succession. This has to be considered in developing algorithms for regional or global mapping of biomass from lidar waveform data.
Workflows for Full Waveform Inversions
NASA Astrophysics Data System (ADS)
Boehm, Christian; Krischer, Lion; Afanasiev, Michael; van Driel, Martin; May, Dave A.; Rietmann, Max; Fichtner, Andreas
2017-04-01
Despite many theoretical advances and the increasing availability of high-performance computing clusters, full seismic waveform inversions still face considerable challenges regarding data and workflow management. While the community has access to solvers which can harness modern heterogeneous computing architectures, the computational bottleneck has fallen to these often manpower-bounded issues that need to be overcome to facilitate further progress. Modern inversions involve huge amounts of data and require a tight integration between numerical PDE solvers, data acquisition and processing systems, nonlinear optimization libraries, and job orchestration frameworks. To this end we created a set of libraries and applications revolving around Salvus (http://salvus.io), a novel software package designed to solve large-scale full waveform inverse problems. This presentation focuses on solving passive source seismic full waveform inversions from local to global scales with Salvus. We discuss (i) design choices for the aforementioned components required for full waveform modeling and inversion, (ii) their implementation in the Salvus framework, and (iii) how it is all tied together by a usable workflow system. We combine state-of-the-art algorithms ranging from high-order finite-element solutions of the wave equation to quasi-Newton optimization algorithms using trust-region methods that can handle inexact derivatives. All is steered by an automated interactive graph-based workflow framework capable of orchestrating all necessary pieces. This naturally facilitates the creation of new Earth models and hopefully sparks new scientific insights. Additionally, and even more importantly, it enhances reproducibility and reliability of the final results.
SXS Catalog of Gravitational Waveforms
NASA Astrophysics Data System (ADS)
Hemberger, Daniel; SXS Collaboration
2015-04-01
Many aspects of gravitational-wave astronomy rely on numerical relativity for accurate models of gravitational waveforms. In recent years, several numerical relativity groups have built catalogs of numerical waveforms from binary black hole systems. I will report on the status of the Simulating Extreme Spacetimes (SXS) waveform catalog, which comprises simulations performed with the Spectral Einstein Code (SpEC). I will describe our approach for assessing numerical errors and convergence. Finally, I will discuss future plans to increase parameter space coverage of the catalog and to improve waveform accuracy.
NASA Technical Reports Server (NTRS)
Ocasio, W. C.; Rigney, D. R.; Clark, K. P.; Mark, R. G.; Goldberger, A. L. (Principal Investigator)
1993-01-01
We describe the theory and computer implementation of a newly-derived mathematical model for analyzing the shape of blood pressure waveforms. Input to the program consists of an ECG signal, plus a single continuous channel of peripheral blood pressure, which is often obtained invasively from an indwelling catheter during intensive-care monitoring or non-invasively from a tonometer. Output from the program includes a set of parameter estimates, made for every heart beat. Parameters of the model can be interpreted in terms of the capacitance of large arteries, the capacitance of peripheral arteries, the inertance of blood flow, the peripheral resistance, and arterial pressure due to basal vascular tone. Aortic flow due to contraction of the left ventricle is represented by a forcing function in the form of a descending ramp, the area under which represents the stroke volume. Differential equations describing the model are solved by the method of Laplace transforms, permitting rapid parameter estimation by the Levenberg-Marquardt algorithm. Parameter estimates and their confidence intervals are given in six examples, which are chosen to represent a variety of pressure waveforms that are observed during intensive-care monitoring. The examples demonstrate that some of the parameters may fluctuate markedly from beat to beat. Our program will find application in projects that are intended to correlate the details of the blood pressure waveform with other physiological variables, pathological conditions, and the effects of interventions.
NASA Technical Reports Server (NTRS)
Ocasio, W. C.; Rigney, D. R.; Clark, K. P.; Mark, R. G.; Goldberger, A. L. (Principal Investigator)
1993-01-01
We describe the theory and computer implementation of a newly-derived mathematical model for analyzing the shape of blood pressure waveforms. Input to the program consists of an ECG signal, plus a single continuous channel of peripheral blood pressure, which is often obtained invasively from an indwelling catheter during intensive-care monitoring or non-invasively from a tonometer. Output from the program includes a set of parameter estimates, made for every heart beat. Parameters of the model can be interpreted in terms of the capacitance of large arteries, the capacitance of peripheral arteries, the inertance of blood flow, the peripheral resistance, and arterial pressure due to basal vascular tone. Aortic flow due to contraction of the left ventricle is represented by a forcing function in the form of a descending ramp, the area under which represents the stroke volume. Differential equations describing the model are solved by the method of Laplace transforms, permitting rapid parameter estimation by the Levenberg-Marquardt algorithm. Parameter estimates and their confidence intervals are given in six examples, which are chosen to represent a variety of pressure waveforms that are observed during intensive-care monitoring. The examples demonstrate that some of the parameters may fluctuate markedly from beat to beat. Our program will find application in projects that are intended to correlate the details of the blood pressure waveform with other physiological variables, pathological conditions, and the effects of interventions.
NASA Astrophysics Data System (ADS)
Hansteen, V.; Murdin, P.
2000-11-01
The SOLAR TRANSITION REGION comprises the PLASMA between the CHROMOSPHERE and the CORONA. In both of these regions the temperature is fairly uniform. The transition region, by contrast, is believed to be characterized by a very steep temperature rise from a chromospheric temperature of slightly less than 104 K to coronal temperatures on the order of 106 K. The goal of modeling the transition regi...
NASA Astrophysics Data System (ADS)
Herrman, M.; Polet, J.
2016-12-01
A total of 73 broadband seismometers were deployed for a passive source seismic experiment called the Los Angeles Syncline Seismic Interferometry Experiment (LASSIE) from September to November of 2014. The purpose of this experiment was to collect high density seismic data for the Los Angeles Basin (LAB) to better understand basin structure and response. This research will use the data collected from LASSIE to assess and refine current velocity models of the LAB using a full waveform modeling approach. To this end we will compare seismograms recorded by LASSIE for a subset of the 53 earthquakes and quarry blasts located by the Southern California Seismic Network (SCSN) that occurred within or near the LAB during the deployment period to synthetic seismograms generated by the Frequency-Wavenumber (FK) code developed by Zhu and Rivera (2002). A first analysis of the data indicates that roughly 25 of the 53 events have waveforms with sufficiently high signal to noise ratio, providing approximately 500 seismograms that are of suitable quality for comparison. We observe significant changes in waveform characteristics between stations with a very small separation distance of approximately 1 km. Focal mechanisms for most of these events have been obtained from Dr. Egill Hauksson (personal communication). We will show comparisons between the broadband velocity waveforms recorded by stations across the LASSIE array and FK synthetics determined for a variety of 1D velocity models that have been developed for the LAB area (such as Hadley and Kanamori, 1977; Hauksson, 1989, 1995 and Magistrale, 1992). The results of these comparisons will be analyzed to provide additional constraints on the subsurface seismic velocity structure within the Los Angeles basin.
Modeling the transition region
NASA Astrophysics Data System (ADS)
Singer, Bart A.
1994-04-01
The calculation of engineering flows undergoing laminar-turbulent transition presents special problems. Mean-flow quantities obey neither the fully laminar nor the fully turbulent correlations. In addition, local maxima in skin friction, wall temperature, and heat transfer often occur near the end of the transition region. Traditionally, modeling this region has been important for the design of turbine blades, where the transition region is long in relation to the chord length of the blade. More recently, the need for better transition-region models has been recognized by designers of hypersonic vehicles where the high Mach number, the low Reynolds number, and the low-disturbance flight environment emphasize the importance of the transition region. Needless to say, a model that might work well for the transitional flows typically found in gas turbines will not necessarily work well for the external surface of a hypersonic vehicle. In Section 2 of this report, some of the important flow features that control the transition region will be discussed. In Section 3, different approaches to the modeling problem will be summarized and cataloged. Fully turbulent flow models will be discussed in detail in Section 4; models specifically designed for transitional flow, in Section 5; and the evaluation of models, in Section 6.
NASA Astrophysics Data System (ADS)
Zhou, Wei; Brossier, Romain; Operto, Stéphane; Virieux, Jean
2015-09-01
Full waveform inversion (FWI) aims to reconstruct high-resolution subsurface models from the full wavefield, which includes diving waves, post-critical reflections and short-spread reflections. Most successful applications of FWI are driven by the information carried by diving waves and post-critical reflections to build the long-to-intermediate wavelengths of the velocity structure. Alternative approaches, referred to as reflection waveform inversion (RWI), have been recently revisited to retrieve these long-to-intermediate wavelengths from short-spread reflections by using some prior knowledge of the reflectivity and a scale separation between the velocity macromodel and the reflectivity. This study presents a unified formalism of FWI, named as Joint FWI, whose aim is to efficiently combine the diving and reflected waves for velocity model building. The two key ingredients of Joint FWI are, on the data side, the explicit separation between the short-spread reflections and the wide-angle arrivals and, on the model side, the scale separation between the velocity macromodel and the short-scale impedance model. The velocity model and the impedance model are updated in an alternate way by Joint FWI and waveform inversion of the reflection data (least-squares migration), respectively. Starting from a crude velocity model, Joint FWI is applied to the streamer seismic data computed in the synthetic Valhall model. While the conventional FWI is stuck into a local minimum due to cycle skipping, Joint FWI succeeds in building a reliable velocity macromodel. Compared with RWI, the use of diving waves in Joint FWI improves the reconstruction of shallow velocities, which translates into an improved imaging at deeper depths. The smooth velocity model built by Joint FWI can be subsequently used as a reliable initial model for conventional FWI to increase the high-wavenumber content of the velocity model.
Renormalized scattering series for frequency-domain waveform modelling of strong velocity contrasts
NASA Astrophysics Data System (ADS)
Jakobsen, M.; Wu, R. S.
2016-08-01
An improved description of scattering and inverse scattering processes in reflection seismology may be obtained on the basis of a scattering series solution to the Helmoltz equation, which allows one to separately model primary and multiple reflections. However, the popular scattering series of Born is of limited seismic modelling value, since it is only guaranteed to converge if the global contrast is relatively small. For frequency-domain waveform modelling of realistic contrasts, some kind of renormalization may be required. The concept of renormalization is normally associated with quantum field theory, where it is absolutely essential for the treatment of infinities in connection with observable quantities. However, the renormalization program is also highly relevant for classical systems, especially when there are interaction effects that act across different length scales. In the scattering series of De Wolf, a renormalization of the Green's functions is achieved by a split of the scattering potential operator into fore- and backscattering parts; which leads to an effective reorganization and partially re-summation of the different terms in the Born series, so that their order better reflects the physics of reflection seismology. It has been demonstrated that the leading (single return) term in the De Wolf series (DWS) gives much more accurate results than the corresponding Born approximation, especially for models with high contrasts that lead to a large accumulation of phase changes in the forward direction. However, the higher order terms in the DWS that are associated with internal multiples have not been studied numerically before. In this paper, we report from a systematic numerical investigation of the convergence properties of the DWS which is based on two new operator representations of the DWS. The first operator representation is relatively similar to the original scattering potential formulation, but more global and explicit in nature. The second
NASA Astrophysics Data System (ADS)
Wang, Xin; Wei, Shengji; Wu, Wenbo
2017-09-01
The 2015Mw 7.8 Gorkha earthquake sequence that unzipped the lower edge of the Main Himalayan Thrust (MHT) in central Nepal provides an exceptional opportunity to understand the fault geometry in this region. However, the limited number of focal mechanisms and the poor horizontal locations and depths of earthquakes in the global catalog impede us from clearly imaging the ruptured MHT. In this study, we generalized the Amplitude Amplification Factor (AAF) method to teleseismic distance that allows us to model the teleseismic P-waves up to 1.5 Hz. We used well-constrained medium-sized earthquakes to establish AAF corrections for teleseismic stations that were later used to invert the high-frequency waveforms of other nearby events. This new approach enables us to invert the focal mechanisms of some early aftershocks, which is challenging by using other long-period methods. With this method, we obtained 12 focal mechanisms more than that in the GCMT catalog. We also modeled the high-frequency teleseismic P-waves and the surface reflection phases (pP and sP) to precisely constrain the depths of the earthquakes. Our results indicate that the uncertainty of the depth estimation is as small as 1-2 km. Finally, we refined the horizontal locations of these aftershocks using carefully hand-picked arrivals. The refined aftershock mechanisms and locations delineate a clear double-ramp geometry of the MHT, with an almost flat décollement sandwiched in between. The flat (dip ∼7 degrees) portion of the MHT is consistent with the coseismic rupture of the mainshock, which has a well-constrained slip distribution. The fault morphology suggests that the ramps, both along the up-dip and down-dip directions, play a significant role in stopping the rupture of the 2015 Gorkha earthquake. Our method can be applied to general subduction zone earthquakes and fault geometry studies.
NASA Astrophysics Data System (ADS)
Fichtner, Andreas; De Wit, Maarten; van Bergen, Manfred
2010-09-01
We provide new insight into the subduction of old continental lithosphere to depths of more than 100 km beneath the Banda arc, based on a spatial correlation of full waveform tomographic images of its lithosphere with He, Pb, Nd and Sr isotope signatures in its arc volcanics. The thickness of the subducted lithosphere of around 200 km coincides with the thickness of Precambrian lithosphere as inferred from surface wave tomography. While the deep subduction of continental material in continent-continent collisions is widely recognised, the analogue process in the arc-continent collision of the Banda region is currently unique. The integrated data suggest that the late Jurassic ocean lithosphere north of the North Australian craton was capable of entraining large volumes of continental lithosphere. The Banda arc example demonstrates that continental lithosphere in arc-continent collisions is not generally preserved, thus increasing the complexity of tectonic reconstructions. In the particular case of Timor, the tomographic images indicate that this island is not located directly above the northern margin of the North Australian craton, and that decoupled oceanic lithosphere must be located at a considerable distance north of Timor, possibly as far north as the northern margin of the volcanically extinct arc sector. The tomographic images combined with isotope data suggest that subduction of the continental lithosphere did not lead to the delamination of its complete crust. A plausible explanation involves delamination within the continental crust, separating upper from lower crustal units. This interpretation is consistent with the existence of a massive accretionary complex on Timor island, with evidence from Pb isotope analysis for lower-crust involvement in arc volcanism; and with the approximate gravitational stability of the subducted lithosphere as inferred from the tomographic images. The subduction of continental lithosphere including crustal material beneath
1977-08-01
For either target model and fixed trans - mit energy, the radar performance decreases as bandwidth increases. The performance decrease with bandwidth...Active Jamming From a radar waveform viewpoint, the wideband barrage jamming environment Is essentially Identical to the thermal noise...nificant radar energy is detected. A quantitative measure of the improvement achievable by wideband techniques is obtained by considering the case
NASA Astrophysics Data System (ADS)
Li, Tao
Consideration of azimuthal anisotropy, at least to an orthorhombic symmetry is important in exploring the naturally fractured and unconventional hydrocarbon reservoirs. Full waveform inversion of multicomponent seismic data can, in principle, provide more robust estimates of subsurface elastic parameters and density than the inversion of single component (P wave) seismic data. In addition, azimuthally dependent anisotropy can only be resolved by carefully studying the multicomponent seismic displacement data acquired and processed along different azimuths. Such an analysis needs an inversion algorithm capable of simultaneously optimizing multiple objectives, one for each data component along each azimuth. In this dissertation, I propose a novel multiobjective methodology using a parallelized version of NSGA II for waveform inversion of multicomponent seismic data along two azimuths. The proposed methodology is also an improvement of the original NSGA II in overall computational efficiency, preservation of population diversity, and rapid sampling of the model space. Next, the proposed methodology is applied on wide azimuth and multicomponent vertical seismic profile (VSP) data to provide reliable estimation of subsurface anisotropy at and near the well location. Prestack waveform inversion was applied to the wide-azimuth multicomponent VSP data acquired at the Wattenberg Field, located in Denver Basin of northeastern Colorado, USA, to characterize the Niobrara formation for azimuthal anisotropy. By comparing the waveform inversion results with an independent study that used a joint slowness-polarization approach to invert the same data, we conclude that the waveform inversion is a reliable tool for inverting the wide-azimuth multicomponent VSP data for anisotropy estimation. Last but not least, an anisotropic elastic three-dimensional scheme for modeling the elastodynamic wavefield is developed in order to go beyond the 1D layering assumption being used in previous
NASA Astrophysics Data System (ADS)
D'Alessandro, Antonino; Mangano, Giorgio; D'Anna, Giuseppe; Luzio, Dario
2013-09-01
In 2009 December, the OBSLab-INGV (Istituto Nazionale di Geofisica e Vulcanologia) deployed an Ocean Bottom Seismometer with Hydrophone (OBS/H) near the epicentral area of the main shock of the Palermo seismic sequence of 2002. The monitoring activity had a total duration of about 8 months. During this experiment, the OBS/H recorded 247 very local microearthquakes, whose local magnitude is between -0.5 and 2.5 and TS - TP delay time between 0.2 and 5 s, almost all of which were undetected by the Italian National Seismic Network. This local microseismicity has been analysed using an innovative clustering technique that exploits the similarity between the waveforms generated by different events. The clustering technique implemented, based on hierarchical agglomerative algorithms, nearest neighbour technique and dendrogram representation, allowed us to identify nine distinct multiplets characterized by a high degree of similarity between the waveforms. The microevents were located through an improved single-station location (SSL) technique based on the polarization analysis of the 3C signals and on the estimation of the TS - TP time. In the new SSL technique, an unbiased covariance matrix was defined and a ray tracer-based determination of the epicentral distance and hypocentral depth was proposed. All the multiplets were generated by events with hypocentres that were very close to each other. However, not all the identified clusters are also clustered in the time-magnitude domain. It was also observed that some multiplets have clouds of hypocentres overlapping each other. These clusters, indistinguishable without the application of a waveforms clustering technique, show differences in the waveforms that must be attributed to differences in the focal mechanisms which generated the waveforms. The local seismic events recorded are typical of a seismicity generated by a volume characterized by a highly complex fracturing pattern and by an important role in the dynamics
Optimal current waveforms for brushless permanent magnet motors
NASA Astrophysics Data System (ADS)
Moehle, Nicholas; Boyd, Stephen
2015-07-01
In this paper, we give energy-optimal current waveforms for a permanent magnet synchronous motor that result in a desired average torque. Our formulation generalises previous work by including a general back-electromotive force (EMF) wave shape, voltage and current limits, an arbitrary phase winding connection, a simple eddy current loss model, and a trade-off between power loss and torque ripple. Determining the optimal current waveforms requires solving a small convex optimisation problem. We show how to use the alternating direction method of multipliers to find the optimal current in milliseconds or hundreds of microseconds, depending on the processor used, which allows the possibility of generating optimal waveforms in real time. This allows us to adapt in real time to changes in the operating requirements or in the model, such as a change in resistance with winding temperature, or even gross changes like the failure of one winding. Suboptimal waveforms are available in tens or hundreds of microseconds, allowing for quick response after abrupt changes in the desired torque. We demonstrate our approach on a simple numerical example, in which we give the optimal waveforms for a motor with a sinusoidal back-EMF, and for a motor with a more complicated, nonsinusoidal waveform, in both the constant-torque region and constant-power region.
Qu, Fujian; Zarubin, Fidel; Wollenzier, Brian; Nikolski, Vladimir P; Efimov, Igor R
2005-02-01
Implantable cardioverter defibrillator studies have established the superiority of biphasic waveforms over monophasic waveforms. However, external defibrillator studies of biphasic waveforms are not as widespread. Our objective was to compare the defibrillation efficacy of clinically used biphasic waveforms, i.e., truncated exponential, rectilinear, and quasi-sinusoidal (Gurvich) waveforms in a fibrillating heart model. Langendorff-perfused rabbit hearts (n = 10) were stained with a voltage-sensitive fluorescent dye, Di-4-ANEPPS. Transmembrane action potentials were optically mapped from the anterior epicardium. We found that the Gurvich waveform was significantly superior (p < 0.05) to the rectilinear and truncated exponential waveforms. The defibrillation thresholds (mean +/- SE) were as follows: Gurvich, 0.25 +/- 0.01 J; rectilinear-1, 0.34 +/- 0.01 J; rectilinear-2, 0.33 +/- 0.01 J; and truncated exponential, 0.32 +/- 0.02 J. Using optically recorded transmembrane responses, we determined the shock-response transfer function, which allowed us to predict the cellular response to waveforms at high accuracy. The passive parallel resistor-capacitor model (RC-model) predicted polarization superiority of the Gurvich waveform in the myocardium with a membrane time constant (taum) of less than 2 ms. The finding of a lower defibrillation threshold with the Gurvich waveform in an in vitro model of external defibrillation suggests that the Gurvich waveform may be important for future external defibrillator designs.
Chua, Yansong; Morrison, Abigail; Helias, Moritz
2015-01-01
Modeling the layer 5 pyramidal neuron as a system of three connected isopotential compartments, the soma, proximal, and distal compartment, with calcium spike dynamics in the distal compartment following first order kinetics, we are able to reproduce in-vitro experimental results which demonstrate the involvement of calcium spikes in action potentials generation. To explore how calcium spikes affect the neuronal output in-vivo, we emulate in-vivo like conditions by embedding the neuron model in a regime of low background fluctuations with occasional large synchronous inputs. In such a regime, a full calcium spike is only triggered by the synchronous events in a threshold like manner and has a stereotypical waveform. Hence, in such a regime, we are able to replace the calcium dynamics with a simpler threshold triggered current of fixed waveform, which is amenable to analytical treatment. We obtain analytically the mean somatic membrane potential excursion due to a calcium spike being triggered while in the fluctuating regime. Our analytical form that accounts for the covariance between conductances and the membrane potential shows a better agreement with simulation results than a naive first order approximation. PMID:26283954
NASA Astrophysics Data System (ADS)
Namegaya, Y.; Ueno, T.; Satake, K.; Tanioka, Y.
2010-12-01
Tsunami waveform inversion is often used to study the source of tsunamigenic earthquakes. In this method, subsurface fault planes are divided into small subfaults, and the slip distribution, then seafloor deformation are estimated. However, it is sometimes difficult to judge the actual fault plane for offshore earthquake such as those along the eastern margin of Japan Sea. We developed an inversion method to estimate vertical seafloor deformation directly from observed tsunami waveforms. The tsunami source area is divided into many nodes, and the vertical seafloor deformation is calculated around each node by using the B-spline functions. The tsunami waveforms are calculated from each node, and used as the Green’s functions for inversion. To stabilize inversion or avoid overestimation of data errors, we introduce smoothing equations like Laplace’s equations. The optimum smoothing strength is estimated from the Akaike’s Bayesian information criterion (ABIC) Method. Advantage of this method is to estimate the vertical seafloor deformation can be estimated without assuming a fault plane. We applied the method to three recent earthquakes around Japan: the 2007 Chuetsu-oki, 2007 Noto Hanto, and 2003 Tokachi-oki earthquakes. The Chuetsu-oki earthquake (M6.8) occurred off the Japan Sea coast of central Japan on 16 July 2007. For this earthquake, complicated aftershock distribution makes it difficult to judge which of the southeast dipping fault or the northwest dipping fault was the actual fault plane. The tsunami inversion result indicates that the uplifted area extends about 10 km from the coastline, and there are two peaks of uplift: about 40 cm in the south and about 20 cm in the north. TheNoto Hanto earthquake (M6.9) occurred off Noto peninsula, also along the Japan Sea coast of central Japan, on 25 March 2007. The inversion result indicates that the uplifted area extends about 10 km off the coast, and the largest uplift amount is more than 40 cm. Location of
Full Waveform Inversion Using Waveform Sensitivity Kernels
NASA Astrophysics Data System (ADS)
Schumacher, Florian; Friederich, Wolfgang
2013-04-01
We present a full waveform inversion concept for applications ranging from seismological to enineering contexts, in which the steps of forward simulation, computation of sensitivity kernels, and the actual inversion are kept separate of each other. We derive waveform sensitivity kernels from Born scattering theory, which for unit material perturbations are identical to the Born integrand for the considered path between source and receiver. The evaluation of such a kernel requires the calculation of Green functions and their strains for single forces at the receiver position, as well as displacement fields and strains originating at the seismic source. We compute these quantities in the frequency domain using the 3D spectral element code SPECFEM3D (Tromp, Komatitsch and Liu, 2008) and the 1D semi-analytical code GEMINI (Friederich and Dalkolmo, 1995) in both, Cartesian and spherical framework. We developed and implemented the modularized software package ASKI (Analysis of Sensitivity and Kernel Inversion) to compute waveform sensitivity kernels from wavefields generated by any of the above methods (support for more methods is planned), where some examples will be shown. As the kernels can be computed independently from any data values, this approach allows to do a sensitivity and resolution analysis first without inverting any data. In the context of active seismic experiments, this property may be used to investigate optimal acquisition geometry and expectable resolution before actually collecting any data, assuming the background model is known sufficiently well. The actual inversion step then, can be repeated at relatively low costs with different (sub)sets of data, adding different smoothing conditions. Using the sensitivity kernels, we expect the waveform inversion to have better convergence properties compared with strategies that use gradients of a misfit function. Also the propagation of the forward wavefield and the backward propagation from the receiver
Chen, Yifan; Zhou, Yu; Murch, Ross; Kosmas, Panagiotis
2017-04-01
To maximize the effect of treatment and minimize the adverse effect on patients, we propose to optimize nanorobots-assisted targeted drug delivery (TDD) for locoregional treatment of tumor from the perspective of touchable communication channel estimation and waveform design. The drug particles are the information molecules; the loading/injection and unloading of the drug correspond to the transmitting and receiving processes; the concentration-time profile of the drug particles administered corresponds to the signaling pulse. Given this analogy, we first propose to use contrast-enhanced microwave imaging (CMI) as a pretherapeutic evaluation technique to determine the pharmacokinetic model of nanorobots-assisted TDD. The CMI system applies an information-theoretic-criteria-based algorithm to estimate drug accumulation in tumor, which is analogous to the estimation of channel impulse response in the communication context. Subsequently, we present three strategies for optimal targeted therapies from the communication waveform design perspective, which are based on minimization of residual drug molecules at the end of each therapeutic session (i.e., inter-symbol interference), maximization of duration when the drug intensity is above a prespecified threshold during each therapeutic session (i.e., non-fade duration), and minimization of average rate that a therapeutic operation is not received correctly at tumor (i.e., bit error rate). Finally, numerical examples are applied to demonstrate the effectiveness of the proposed analytical framework.
NASA Astrophysics Data System (ADS)
Chang, Jiaqing; Liu, Yaxin; Huang, Bo
2017-07-01
In inkjet applications, it is normal to search for an optimal drive waveform when dispensing a fresh fluid or adjusting a newly fabricated print-head. To test trial waveforms with different dwell times, a camera and a strobe light were used to image the protruding or retracting liquid tongues without ejecting any droplets. An edge detection method was used to calculate the lengths of the liquid tongues to draw the meniscus movement curves. The meniscus movement is determined by the time-domain response of the acoustic pressure at the nozzle of the print-head. Starting at the inverse piezoelectric effect, a mathematical model which considers the liquid viscosity in acoustic propagation is constructed to study the acoustic pressure response at the nozzle of the print-head. The liquid viscosity retards the propagation speed and dampens the harmonic amplitude. The pressure response, which is the combined effect of the acoustic pressures generated during the rising time and the falling time and after their propagations and reflections, explains the meniscus movements well. Finally, the optimal dwell time for droplet ejections is discussed.
NASA Astrophysics Data System (ADS)
He, Y.-X.; Angus, D. A.; Blanchard, T. D.; Wang, G.-L.; Yuan, S.-Y.; Garcia, A.
2016-04-01
Extraction of fluids from subsurface reservoirs induces changes in pore pressure, leading not only to geomechanical changes, but also perturbations in seismic velocities and hence observable seismic attributes. Time-lapse seismic analysis can be used to estimate changes in subsurface hydromechanical properties and thus act as a monitoring tool for geological reservoirs. The ability to observe and quantify changes in fluid, stress and strain using seismic techniques has important implications for monitoring risk not only for petroleum applications but also for geological storage of CO2 and nuclear waste scenarios. In this paper, we integrate hydromechanical simulation results with rock physics models and full-waveform seismic modelling to assess time-lapse seismic attribute resolution for dynamic reservoir characterization and hydromechanical model calibration. The time-lapse seismic simulations use a dynamic elastic reservoir model based on a North Sea deep reservoir undergoing large pressure changes. The time-lapse seismic traveltime shifts and time strains calculated from the modelled and processed synthetic data sets (i.e. pre-stack and post-stack data) are in a reasonable agreement with the true earth models, indicating the feasibility of using 1-D strain rock physics transform and time-lapse seismic processing methodology. Estimated vertical traveltime shifts for the overburden and the majority of the reservoir are within ±1 ms of the true earth model values, indicating that the time-lapse technique is sufficiently accurate for predicting overburden velocity changes and hence geomechanical effects. Characterization of deeper structure below the overburden becomes less accurate, where more advanced time-lapse seismic processing and migration is needed to handle the complex geometry and strong lateral induced velocity changes. Nevertheless, both migrated full-offset pre-stack and near-offset post-stack data image the general features of both the overburden and
NASA Astrophysics Data System (ADS)
Tsuboi, S.; Nakamura, T.; Miyoshi, T.
2015-12-01
May 30, 2015 Bonin Islands, Japan earthquake (Mw 7.8, depth 679.9km GCMT) was one of the deepest earthquakes ever recorded. We apply the waveform inversion technique (Kikuchi & Kanamori, 1991) to obtain slip distribution in the source fault of this earthquake in the same manner as our previous work (Nakamura et al., 2010). We use 60 broadband seismograms of IRIS GSN seismic stations with epicentral distance between 30 and 90 degrees. The broadband original data are integrated into ground displacement and band-pass filtered in the frequency band 0.002-1 Hz. We use the velocity structure model IASP91 to calculate the wavefield near source and stations. We assume that the fault is squared with the length 50 km. We obtain source rupture model for both nodal planes with high dip angle (74 degree) and low dip angle (26 degree) and compare the synthetic seismograms with the observations to determine which source rupture model would explain the observations better. We calculate broadband synthetic seismograms with these source propagation models using the spectral-element method (Komatitsch & Tromp, 2001). We use new Earth Simulator system in JAMSTEC to compute synthetic seismograms using the spectral-element method. The simulations are performed on 7,776 processors, which require 1,944 nodes of the Earth Simulator. On this number of nodes, a simulation of 50 minutes of wave propagation accurate at periods of 3.8 seconds and longer requires about 5 hours of CPU time. Comparisons of the synthetic waveforms with the observation at teleseismic stations show that the arrival time of pP wave calculated for depth 679km matches well with the observation, which demonstrates that the earthquake really happened below the 660 km discontinuity. In our present forward simulations, the source rupture model with the low-angle fault dipping is likely to better explain the observations.
The mechanical waveform of the basilar membrane. II. From data to models--and back.
de Boer, E; Nuttall, A L
2000-03-01
Mechanical responses in the basal turn of the guinea-pig cochlea are measured with low-level broad-band noise as the acoustical stimulus [for details see de Boer and Nuttall, J. Acoust. Soc. Am. 101, 3583-3592 (1997)]. Results are interpreted within the framework of a classical three-dimensional model of the cochlea that belongs to a very wide class of nonlinear models. The use of linear-systems analysis for this class of nonlinear models has been justified earlier [de Boer, Audit. Neurosci. 3, 377-388 (1997)]. The data are subjected to inverse analysis with the aim to recover the "effective basilar-membrane impedance." This is a parameter function that, when inserted into the model, produces a model response, the "resynthesized" response, that is similar to the measured response. With present-day solution methods, resynthesis leads back to an almost perfect replica of the original response in the spatial domain. It is demonstrated in this paper that this also applies to the response in the frequency domain and in the time domain. This paper further reports details with regard to geometrical properties of the model employed. Two three-dimensional models are studied; one has its dimensions close to that of the real cochlea, the other is a stylized model which has homogeneous geometry over its length. In spite of the geometric differences the recovered impedance functions are very similar. An impedance function computed for one model can be used in resynthesis of the response in the other one, and this leads to global amplitude deviations between original and resynthesized response functions not exceeding 8 dB. Discrepancies are much larger (particularly in the phase) when a two-dimensional model is compared with a three-dimensional model. It is concluded that a stylized three-dimensional model with homogeneous geometric parameters will give sufficient information in further work on unraveling cochlear function via inverse analysis. In all cases of a sensitive
NASA Astrophysics Data System (ADS)
Rhie, J.; Kim, S.; Lee, S.
2012-12-01
We construct a preliminary 3D seismic velocity model for the crust beneath the southern part of the Korean Peninsula. Broadband waveforms obtained from seismic network in and around the study area are used. First, a quasi-3D S-wave model is estimated from Rayleigh wave tomography using ambient seismic noise. During the depth-inversion of dispersion curve for each inversion node, a Bayesian approach is used to introduce sharp boundaries and to provide a statistical assessment of inverted 1D Vsv models. Crustal thickness and average Vp/Vs ratio are constrained from the result of previous receiver function (RF) study. Then, Love wave dispersions are inverted for 1D Vsh models by allowing small velocity perturbations with respect to the previously defined 1D Vsv-wave models. Lastly, a series of forward 3D waveform modeling are performed based on the anisotropic S-wave model. The starting P-wave velocity model is determined by using Vp/Vs ratio from the RF study and an average model between Vsv and Vsh models. Values of Vp/Vs ratio, Vsv, Vsh, and crustal thickness are systematically varied during the forward modeling to fit observed three-component broadband (~0.05-0.3 Hz) waveforms. By doing this, we develop a preliminary 3D velocity model for the southern Korean Peninsula. Our model is a starting model of the realistic 3D model, which takes into account more data such as surface geological feature, high-frequency body wave travel times, and gravity. The final model will be used to predict strong g round motion of potential large scenario earthquakes after correcting site effects.
NASA Astrophysics Data System (ADS)
Afanasiev, Michael; Boehm, Christian; van Driel, Martin; Krischer, Lion; May, Dave; Rietmann, Max; Fichtner, Andreas
2017-04-01
Recent years have been witness to the application of waveform inversion to new and exciting domains, ranging from non-destructive testing to global seismology. Often, each new application brings with it novel wave propagation physics, spatial and temporal discretizations, and models of variable complexity. Adapting existing software to these novel applications often requires a significant investment of time, and acts as a barrier to progress. To combat these problems we introduce Salvus, a software package designed to solve large-scale full-waveform inverse problems, with a focus on both flexibility and performance. Currently based on an abstract implementation of high order finite (spectral) elements, we have built Salvus to work on unstructured quad/hex meshes in both 2 or 3 dimensions, with support for P1-P3 bases on triangles and tetrahedra. A diverse (and expanding) collection of wave propagation physics are supported (i.e. viscoelastic, coupled solid-fluid). With a focus on the inverse problem, functionality is provided to ease integration with internal and external optimization libraries. Additionally, a python-based meshing package is included to simplify the generation and manipulation of regional to global scale Earth models (quad/hex), with interfaces available to external mesh generators for complex engineering-scale applications (quad/hex/tri/tet). Finally, to ensure that the code remains accurate and maintainable, we build upon software libraries such as PETSc and Eigen, and follow modern software design and testing protocols. Salvus bridges the gap between research and production codes with a design based on C++ template mixins and Python wrappers that separates the physical equations from the numerical core. This allows domain scientists to add new equations using a high-level interface, without having to worry about optimized implementation details. Our goal in this presentation is to introduce the code, show several examples across the scales, and
Global and local waveform simulations using the VERCE platform
NASA Astrophysics Data System (ADS)
Garth, Thomas; Saleh, Rafiq; Spinuso, Alessandro; Gemund, Andre; Casarotti, Emanuele; Magnoni, Federica; Krischner, Lion; Igel, Heiner; Schlichtweg, Horst; Frank, Anton; Michelini, Alberto; Vilotte, Jean-Pierre; Rietbrock, Andreas
2017-04-01
In recent years the potential to increase resolution of seismic imaging by full waveform inversion has been demonstrated on a range of scales from basin to continental scales. These techniques rely on harnessing the computational power of large supercomputers, and running large parallel codes to simulate the seismic wave field in a three-dimensional geological setting. The VERCE platform is designed to make these full waveform techniques accessible to a far wider spectrum of the seismological community. The platform supports the two widely used spectral element simulation programs SPECFEM3D Cartesian, and SPECFEM3D globe, allowing users to run a wide range of simulations. In the SPECFEM3D Cartesian implementation the user can run waveform simulations on a range of pre-loaded meshes and velocity models for specific areas, or upload their own velocity model and mesh. In the new SPECFEM3D globe implementation, the user will be able to select from a number of continent scale model regions, or perform waveform simulations for the whole earth. Earthquake focal mechanisms can be downloaded within the platform, for example from the GCMT catalogue, or users can upload their own focal mechanism catalogue through the platform. The simulations can be run on a range of European supercomputers in the PRACE network. Once a job has been submitted and run through the platform, the simulated waveforms can be manipulated or downloaded for further analysis. The misfit between the simulated and recorded waveforms can then be calculated through the platform through three interoperable workflows, for raw-data access (FDSN) and caching, pre-processing and finally misfit. The last workflow makes use of the Pyflex analysis software. In addition, the VERCE platform can be used to produce animations of waveform propagation through the velocity model, and synthetic shakemaps. All these data-products are made discoverable and re-usable thanks to the VERCE data and metadata management layer. We
Modeling Regional Seismic Waves
1992-06-29
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NASA Astrophysics Data System (ADS)
Beachly, M. W.; Hooft, E. E.; Toomey, D. R.; Waite, G. P.
2011-12-01
Imaging magmatic systems improves our understanding of magma ascent and storage in the crust and contributes to hazard assessment. Seismic tomography reveals crustal magma bodies as regions of low velocity; however the ability of delay-time tomography to detect small, low-velocity bodies is limited by wavefront healing. Alternatively, crustal magma chambers have been identified from secondary phases including P and S wave reflections and conversions. We use a combination of P-wave tomography and finite-difference waveform modeling to characterize a shallow crustal magma body at Newberry Volcano, central Oregon. Newberry's eruptions are silicic within the central caldera and mafic on its periphery suggesting a central silicic magma storage system. The system may still be active with a recent eruption ~1300 years ago and a drill hole temperature of 256° C at only 932 m depth. A low-velocity anomaly previously imaged at 3-5 km beneath the caldera indicates either a magma body or a fractured pluton. With the goal of detecting secondary arrivals from a magma chamber beneath Newberry Volcano, we deployed a line of densely-spaced (~300 m), three-component seismometers that recorded a shot of opportunity from the High Lava Plains Experiment in 2008. The data record a secondary P-wave arrival originating from beneath the caldera. In addition we combine travel-time data from our 2008 experiment with data collected in the 1980's by the USGS for a P-wave tomography inversion to image velocity structure to 6 km depth. The inversion includes 16 active sources, 322 receivers and 1007 P-wave first arrivals. The tomography results reveal a high-velocity, ring-like anomaly beneath the caldera ring faults to 2 km depth that surrounds a shallow low-velocity region. Beneath 2.5 km high-velocity anomalies are concentrated east and west of the caldera. A central low-velocity body lies below 3 km depth. Tomographic inversions of synthetic data suggest that the central low-velocity body
Partitioned Waveform Inversion Applied to Eurasia and Northern Africa
bedle, H; Matzel, E; Flanagan, M
2006-07-27
This report summarizes the data analysis achieved during Heather Bedle's eleven-week Technical Scholar internship at Lawrence Livermore National Labs during the early summer 2006. The work completed during this internship resulted in constraints on the crustal and upper mantle S-velocity structure in Northern Africa, the Mediterranean, the Middle East, and Europe, through the fitting of regional waveform data. This data extends current raypath coverage and will be included in a joint inversion along with data from surface wave group velocity measurements, S and P teleseismic arrival time data, and receiver function data to create an improved velocity model of the upper mantle in this region. The tectonic structure of the North African/Mediterranean/Europe/Middle Eastern study region is extremely heterogeneous. This region consists of, among others, stable cratons and platforms such as the West Africa Craton, and Baltica in Northern Europe; oceanic subduction zones throughout the Mediterranean Sea where the African and Eurasian plate collide; regions of continental collision as the Arabian Plate moves northward into the Turkish Plate; and rifting in the Red Sea, separating the Arabian and Nubian shields. With such diverse tectonic structures, many of the waveforms were difficult to fit. This is not unexpected as the waveforms are fit using an averaged structure. In many cases the raypaths encounter several tectonic features, complicating the waveform, and making it hard for the software to converge on a 1D average structure. Overall, the quality of the waveform data was average, with roughly 30% of the waveforms being discarded due to excessive noise that interfered with the frequency ranges of interest. An inversion for the 3D S-velocity structure of this region was also performed following the methodology of Partitioned Waveform Inversion (Nolet, 1990; Van der Lee and Nolet, 1997). The addition of the newly fit waveforms drastically extends the range of the model
3-D Waveform Modeling of the 11 September 2001 World Trade Center Collapse Events in New York City
NASA Astrophysics Data System (ADS)
Yoo, S.; Rhie, J.; Kim, W.
2010-12-01
The seismic signals from collapse of the twin towers of World Trade Center (WTC), NYC were well recorded by the seismographic stations in the northeastern United States. The building collapse can be represented by a vertical single force which does not generate tangential component seismic signals during the source process. The waveforms recorded by the Basking Ridge, NJ (BRNJ) station located due west of the WTC site show that the amplitude on tangential component is negligible and indicates that a vertical single force assumption is valid and the velocity structure is more or less homogeneous along the propagation path. However, 3-component seismograms recorded at Palisades, NY (PAL), which is located 33.8 km due north of the WTC site along the Hudson River (azimuth = 15.2°), show abnormal features. The amplitude on tangential component is larger than on vertical- or on radial-component. This observation may be attributable to the complex energy conversion between Rayleigh and Love waves due to the strong low velocity anomaly associated with unconsolidated sediments under the Hudson River. To test the effects of the low velocity anomaly on the enhanced amplitude in tangential component, we developed a 3D velocity model by considering local geology such as unconsolidated sediment layer, Palisades sill, Triassic sandstone, and crystalline basement and simulated waveforms at PAL. The preliminary synthetic results show that 3D velocity structure can significantly enhance the amplitude in tangential component but it is not as large as the observation. Although a more precise 3D model is required to better explain the observations, our results confirm that the low velocity layer under the Hudson River can enhance the amplitude in tangential component at PAL. This result suggests that a good understanding of the amplitude enhancements for specific event-site pairs may be important to evaluate seismic hazard of metropolitan New York City.
NASA Astrophysics Data System (ADS)
Reiss, M. C.; Rümpker, G.; Tilmann, F.; Yuan, X.; Giese, J.; Rindraharisaona, E. J.
2016-09-01
Madagascar occupies a key position in the assembly and breakup of the supercontinent Gondwana. It has been used in numerous geological studies to reconstruct its original position within Gondwana and to derive plate kinematics. Seismological observations in Madagascar to date have been sparse. Using a temporary, dense seismic profile across southern Madagascar, we present the first published study of seismic anisotropy from shear wave splitting analyses of teleseismic phases. The splitting parameters obtained show significant small-scale variation of fast polarization directions and delay times across the profile, with fast polarization rotating from NW in the center to NE in the east and west of the profile. The delay times range between 0.4 and 1.5 s. A joint inversion of waveforms at each station is applied to derive hypothetical one-layer splitting parameters. We use finite-difference, full-waveform modeling to test several hypotheses about the origin and extent of seismic anisotropy. Our observations can be explained by asthenospheric anisotropy with a fast polarization direction of 50°, approximately parallel to the absolute plate motion direction, in combination with blocks of crustal anisotropy. Predictions of seismic anisotropy as inferred from global mantle flow models or global anisotropic surface wave tomography are not in agreement with the observations. Small-scale variations of splitting parameters require significant crustal anisotropy. Considering the complex geology of Madagascar, we interpret the change in fast-axis directions as a 150 km wide zone of ductile deformation in the crust as a result of the intense reworking of lithospheric material during the Pan-African orogeny. This fossil anisotropic pattern is underlain by asthenospheric anisotropy induced by plate motion.
Visualization and analysis of lidar waveform data
NASA Astrophysics Data System (ADS)
Olsen, Richard C.; Metcalf, Jeremy P.
2017-05-01
LiDAR waveform analysis is a relatively new activity in the area of laser scanning. The work described here is an exploration of a different approach to visualization and analysis, following the structure that has evolved for the analysis of imaging spectroscopy data (hyperspectral imaging). The waveform data are transformed into 3-dimensional data structures that provide xy position information, and a z-coordinate, which is the digitized waveform. This allows for representation of the data in spatial and waveform space, the extraction of characteristic spectra, and the development of regions of interest. This representation allows for the application of standard spectral classification tools such as the maximum likelihood classifier.
NASA Astrophysics Data System (ADS)
Moulik, P.; Ekström, G.
2014-12-01
We use normal-mode splitting functions in addition to surface wave phase anomalies, body wave traveltimes and long-period waveforms to construct a 3-D model of anisotropic shear wave velocity in the Earth's mantle. Our modelling approach inverts for mantle velocity and anisotropy as well as transition-zone discontinuity topographies, and incorporates new crustal corrections for the splitting functions that are consistent with the non-linear corrections we employ for the waveforms. Our preferred anisotropic model, S362ANI+M, is an update to the earlier model S362ANI, which did not include normal-mode splitting functions in its derivation. The new model has stronger isotropic velocity anomalies in the transition zone and slightly smaller anomalies in the lowermost mantle, as compared with S362ANI. The differences in the mid- to lowermost mantle are primarily restricted to features in the Southern Hemisphere. We compare the isotropic part of S362ANI+M with other recent global tomographic models and show that the level of agreement is higher now than in the earlier generation of models, especially in the transition zone and the lower mantle. The anisotropic part of S362ANI+M is restricted to the upper 300 km in the mantle and is similar to S362ANI. When radial anisotropy is allowed throughout the mantle, large-scale anisotropic patterns are observed in the lowermost mantle with vSV > vSH beneath Africa and South Pacific and vSH > vSV beneath several circum-Pacific regions. The transition zone exhibits localized anisotropic anomalies of ˜3 per cent vSH > vSV beneath North America and the Northwest Pacific and ˜2 per cent vSV > vSH beneath South America. However, small improvements in fits to the data on adding anisotropy at depth leave the question open on whether large-scale radial anisotropy is required in the transition zone and in the lower mantle. We demonstrate the potential of mode-splitting data in reducing the trade-offs between isotropic velocity and
NASA Astrophysics Data System (ADS)
Alzahrany, Mohammed; Banerjee, Arindam
2012-11-01
A computational fluid dynamic study is carried out to investigate gas transport in patient specific human lung models (based on CT scans) during high frequency oscillatory ventilation (HFOV). Different pressure-controlled waveforms and various ventilator frequencies are studied to understand the effect of flow transport and gas mixing during these processes. Three different pressure waveforms are created by solving the equation of motion subjected to constant lung wall compliance and flow resistance. Sinusoidal, exponential and constant waveforms shapes are considered with three different frequencies 6, 10 and 15 Hz and constant tidal volume 50 ml. The velocities are calculated from the obtained flow rate and imposed as inlet flow conditions to represent the mechanical ventilation waveforms. An endotracheal tube ETT is joined to the model to account for the effect of the invasive management device with the peak Reynolds number (Re) for all the cases ranging from 6960 to 24694. All simulations are performed using high order LES turbulent model. The gas transport near the flow reversal will be discussed at different cycle phases for all the cases and a comparison of the secondary flow structures between different cases will be presented.
NASA Astrophysics Data System (ADS)
Rhode, Kawal; Lambrou, Tryphon; Seifalian, Alexander M.; Hawkes, David J.
2002-04-01
We have developed a waveform shape model-based algorithm for the extraction of blood flow from dynamic arterial x-ray angiographic images. We have carried out in-vitro validation of this technique. A pulsatile physiological blood flow circuit was constructed using an anthropomorphic cerebral vascular phantom to simulate the cerebral arterial circulation with whole blood as the fluid. Instantaneous recording of flow from an electromagnetic flow meter (EMF) provided the gold standard measurement. Biplane dynamic digital x-ray images of the vascular phantom with injection of contrast medium were acquired at 25 fps using a PC frame capture card with calibration using a Perspex cube. Principal component analysis was used to construct a shape model by collecting 434 flow waveforms from the EMF under varying flow conditions. Blood flow waveforms were calculated from the angiographic data by using our previous concentration-distance curve matching (ORG) algorithm and by using the new model-based (MB) algorithm. Both instantaneous and mean flow values calculated using the MB algorithm showed greater correlation, less bias, and lower variability than those calculated using the ORG algorithm when compared to the EMF values. We have successfully demonstrated that use of a priori waveform shape information can improve flow measurements from dynamic x-ray angiograms.
NASA Astrophysics Data System (ADS)
Pürrer, Michael
2016-03-01
I provide a frequency domain reduced order model (ROM) for the aligned-spin effective-one-body model "SEOBNRv2" for data analysis with second- and third-generation ground-based gravitational wave (GW) detectors. SEOBNRv2 models the dominant mode of the GWs emitted by the coalescence of black hole binaries. The large physical parameter space (dimensionless spins -1 ≤χi≤0.99 and symmetric mass ratios 0.01 ≤η ≤0.25 ) requires sophisticated reduced order modeling techniques, including patching in the parameter space and in frequency. I find that the time window over which the inspiral-plunge and the merger-ringdown waveform in SEOBNRv2 are connected has a discontinuous dependence on the parameters when the spin parameter χ =0.8 or the symmetric mass ratio η ˜0.083 . This discontinuity increases resolution requirements for the ROM. The ROM can be used for compact binary systems with total masses of 2 M⊙ or higher for the Advanced LIGO design sensitivity and a 10 Hz lower cutoff frequency. The ROM has a worst mismatch against SEOBNRv2 of ˜1 %, but in general mismatches are better than ˜0.1 %. The ROM is crucial for key data analysis applications for compact binaries, such as GW searches and parameter estimation carried out within the LIGO Scientific Collaboration.
NASA Astrophysics Data System (ADS)
Malovichko, M.; Khokhlov, N.; Yavich, N.; Zhdanov, M.
2017-10-01
Over the recent decades, a number of fast approximate solutions of Lippmann-Schwinger equation, which are more accurate than classic Born and Rytov approximations, were proposed in the field of electromagnetic modeling. Those developments could be naturally extended to acoustic and elastic fields; however, until recently, they were almost unknown in seismology. This paper presents several solutions of this kind applied to acoustic modeling for both lossy and lossless media. We evaluated the numerical merits of those methods and provide an estimation of their numerical complexity. In our numerical realization we use the matrix-free implementation of the corresponding integral operator. We study the accuracy of those approximate solutions and demonstrate, that the quasi-analytical approximation is more accurate, than the Born approximation. Further, we apply the quasi-analytical approximation to the solution of the inverse problem. It is demonstrated that, this approach improves the estimation of the data gradient, comparing to the Born approximation. The developed inversion algorithm is based on the conjugate-gradient type optimization. Numerical model study demonstrates that the quasi-analytical solution significantly reduces computation time of the seismic full-waveform inversion. We also show how the quasi-analytical approximation can be extended to the case of elastic wavefield.
Simple Waveforms, Simply Described
NASA Technical Reports Server (NTRS)
Baker, John G.
2008-01-01
Since the first Lazarus Project calculations, it has been frequently noted that binary black hole merger waveforms are 'simple.' In this talk we examine some of the simple features of coalescence and merger waveforms from a variety of binary configurations. We suggest an interpretation of the waveforms in terms of an implicit rotating source. This allows a coherent description, of both the inspiral waveforms, derivable from post-Newtonian(PN) calculations, and the numerically determined merger-ringdown. We focus particularly on similarities in the features of various Multipolar waveform components Generated by various systems. The late-time phase evolution of most L these waveform components are accurately described with a sinple analytic fit. We also discuss apparent relationships among phase and amplitude evolution. Taken together with PN information, the features we describe can provide an approximate analytic description full coalescence wavefoRms. complementary to other analytic waveforns approaches.
NASA Astrophysics Data System (ADS)
Budzisz, Joanna; Wróblewski, Zbigniew
2016-03-01
The article presents a method of modelling a vaccum circuit breaker in the ATP/EMTP package, the results of the verification of the correctness of the developed digital circuit breaker model operation and its practical usefulness for analysis of overvoltages and overcurrents occurring in commutated capacitive electrical circuits and also examples of digital simulations of overvoltages and overcurrents in selected electrical circuits.
NASA Astrophysics Data System (ADS)
Kim, Keehoon; Rodgers, Arthur
2017-08-01
Vertical stratification in the low atmosphere impacts near-ground sound propagation. On clear days, for example, negative gradients of low-atmospheric temperature can lead to upward refraction of acoustic waves and create a zone of silence near the ground, where no acoustic rays can arrive. We investigate impacts of lower tropospheric temperature and wind-velocity gradient on acoustic wave propagation using numerical simulations. Sound refraction in the atmosphere is a frequency-dependent wave phenomenon, and therefore classical ray methods based on infinite-frequency approximation may not be suitable for modeling acoustic wave amplitudes. In this study, a full-waveform acoustic solver was used to predict amplitudes of acoustic waves taking into account meteorological conditions (temperature, pressure and wind). Local radiosonde sounding data were input into acoustic simulations to characterize the background conditions of the local atmosphere. The results of numerical modeling indicate that acoustic overpressure amplitudes were significantly affected by local atmospheric wind speed and direction near the ground. Local wind changes the effective sound speed profile in the atmosphere and influences overpressure amplitude decay governed by upward refraction. We compared 3-D finite-difference modeling results with acoustic overpressure measurements from the Humming Roadrunner explosion experiments conducted in New Mexico in 2012. The modeling results showed good agreement with the observations in peak amplitudes when a background wind was weak and well characterized by local atmospheric data. However, when a strong wind was present at an explosion and its variability was poorly characterized by local radiosonde sounding, the numerical prediction of local acoustic amplitude agreed poorly with the observations. Additional numerical simulations with the inclusion of surface wind data indicate that local acoustic amplitudes could be significantly variable depending on
NASA Astrophysics Data System (ADS)
Lin, Ying
2005-09-01
It is commonly held that an important aspect of early phonological acquisition is the ability to learn sound distributions, or statistical learning. Yet significant differences in lexical representations are often observed in studies of infant speech perception, suggesting a protracted process of phonological development. The goal of the current project is to develop a model that links holistic and segmental representation of spoken words, using tools from contemporary speech recognition. In the present stage, the model focuses on the pre-lexical level of phonological development, and tries to identify segmental representations from acoustic signals of isolated words. The segmental representations are based on units that correspond to acoustic phonetic classes, and learning involves updating the unit models in parallel with updating phonotactics. Starting from acoustic segmentations, the model iteratively updates knowledge of the units and phonotactics, and renews segmentation hypotheses regarding each word until convergence. The results of running this algorithm on TIMIT and infant-directed speech data suggest that the model approximately identifies segment-sized broad classes in an unsupervised manner. This statistical approach also provides a different perspective on the role of lexicon in phonological development.
Reconstruction of audio waveforms from spike trains of artificial cochlea models
Zai, Anja T.; Bhargava, Saurabh; Mesgarani, Nima; Liu, Shih-Chii
2015-01-01
Spiking cochlea models describe the analog processing and spike generation process within the biological cochlea. Reconstructing the audio input from the artificial cochlea spikes is therefore useful for understanding the fidelity of the information preserved in the spikes. The reconstruction process is challenging particularly for spikes from the mixed signal (analog/digital) integrated circuit (IC) cochleas because of multiple non-linearities in the model and the additional variance caused by random transistor mismatch. This work proposes an offline method for reconstructing the audio input from spike responses of both a particular spike-based hardware model called the AEREAR2 cochlea and an equivalent software cochlea model. This method was previously used to reconstruct the auditory stimulus based on the peri-stimulus histogram of spike responses recorded in the ferret auditory cortex. The reconstructed audio from the hardware cochlea is evaluated against an analogous software model using objective measures of speech quality and intelligibility; and further tested in a word recognition task. The reconstructed audio under low signal-to-noise (SNR) conditions (SNR < –5 dB) gives a better classification performance than the original SNR input in this word recognition task. PMID:26528113
FAST TRACK PAPER: Resolving crustal thickness using SS waveform stacks
NASA Astrophysics Data System (ADS)
Rychert, Catherine A.; Shearer, Peter M.
2010-03-01
We image lithospheric interfaces using variations in the character of SS waveform stacks, a method we term SS Lithospheric Interface Profiling (SSLIP). The variations are caused by reflected phases, that is, underside reflections (SS precursors) and topside multiples (SS reverberations), created at velocity discontinuities near the midpoint of the SS ray path. Stacks from continental versus oceanic bounce point regions produce distinctly different SS waveforms, consistent with the large continent/ocean difference in crustal thickness. To investigate the potential of SS waveform stacks to constrain Moho depths under continents, we develop a method to fit continental bounce point stacks with a reference SS waveform convolved with a crustal operator. The SSLIP inferred Moho depths agree with the CRUST 2.0 model in Asia for those regions where the SS bounce point density is the highest. The SSLIP depths are correlated (correlation coefficient 0.82) with the CRUST 2.0 values averaged over sample bins of 10° radius. The SSLIP method has broad lateral resolution in comparison to most other methods for resolving crustal thickness, but has the potential to sample regions where station coverage may be sparse.
This report describes a system for storing an arbitrary waveform on non-volatile random access memory ( NVRAM ) device and generating an analog signal...using the NVRAM device. A central processing unit is used to synthesize an arbitrary waveform and create a digital representation of the waveform and...transfer the digital representation to a microprocessor which, in turn, writes the digital data into an NVRAM device which has been mapped into a
A theoretical model of the endothelial cell morphology due to different waveforms.
Sáez, P; Malvè, M; Martínez, M A
2015-08-21
Endothelial cells are key units in the regulatory biological process of blood vessels. They represent an interface to transmit variations on the fluid dynamic changes. They are able to adapt its cytoskeleton, by means of microtubules reorientation and F-actin reorganization, due to new mechanical environments. Moreover, they are responsible for initiating a huge cascade of biological processes, such as the release of endothelins (ET-1), in charge of the constriction of the vessel and growth factors such as TGF-β and PDGF. Although a huge efforts have been made in the experimental characterization and description of these two issues the computational modeling has not gained such an attention. In this work we study the 3D remodeling of endothelial cells based on the main features of blood flow. In particular we study how different oscillatory shear index and the time average wall shear stresses modify the endothelial cell shape. We found our model fitted the experimental works presented before in in vitro studies. We also include our model within a computational fluid dynamics simulation of a carotid artery to evaluate endothelial cell shape index which is a key predictor of atheroma plaque formation. Moreover, our approach can be coupled with models of collagen and smooth muscle cell growth, where remodeling and the associated release of chemical substance are involved. Copyright © 2015 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Fabien-Ouellet, Gabriel; Gloaguen, Erwan; Giroux, Bernard
2017-03-01
Full Waveform Inversion (FWI) aims at recovering the elastic parameters of the Earth by matching recordings of the ground motion with the direct solution of the wave equation. Modeling the wave propagation for realistic scenarios is computationally intensive, which limits the applicability of FWI. The current hardware evolution brings increasing parallel computing power that can speed up the computations in FWI. However, to take advantage of the diversity of parallel architectures presently available, new programming approaches are required. In this work, we explore the use of OpenCL to develop a portable code that can take advantage of the many parallel processor architectures now available. We present a program called SeisCL for 2D and 3D viscoelastic FWI in the time domain. The code computes the forward and adjoint wavefields using finite-difference and outputs the gradient of the misfit function given by the adjoint state method. To demonstrate the code portability on different architectures, the performance of SeisCL is tested on three different devices: Intel CPUs, NVidia GPUs and Intel Xeon PHI. Results show that the use of GPUs with OpenCL can speed up the computations by nearly two orders of magnitudes over a single threaded application on the CPU. Although OpenCL allows code portability, we show that some device-specific optimization is still required to get the best performance out of a specific architecture. Using OpenCL in conjunction with MPI allows the domain decomposition of large models on several devices located on different nodes of a cluster. For large enough models, the speedup of the domain decomposition varies quasi-linearly with the number of devices. Finally, we investigate two different approaches to compute the gradient by the adjoint state method and show the significant advantages of using OpenCL for FWI.
Waveform modeling of the seismic response of a mid-ocean ridge axial melt sill
NASA Astrophysics Data System (ADS)
Xu, Min; Stephen, R. A.; Canales, J. Pablo
2017-02-01
Seismic reflections from axial magma lens (AML) are commonly observed along many mid-ocean ridges, and are thought to arise from the negative impedance contrast between a solid, high-speed lid and the underlying low-speed, molten or partially molten (mush) sill. The polarity of the AML reflection (P AML P) at vertical incidence and the amplitude vs offset (AVO) behavior of the AML reflections (e.g., P AML P and S-converted P AML S waves) are often used as a diagnostic tool for the nature of the low-speed sill. Time-domain finite difference calculations for two-dimensional laterally homogeneous models show some scenarios make the interpretation of melt content from partial-offset stacks of P- and S-waves difficult. Laterally heterogeneous model calculations indicate diffractions from the edges of the finite-width AML reducing the amplitude of the AML reflections. Rough seafloor and/or a rough AML surface can also greatly reduce the amplitude of peg-leg multiples because of scattering and destructive interference. Mid-crustal seismic reflection events are observed in the three-dimensional multi-channel seismic dataset acquired over the RIDGE-2000 Integrated Study Site at East Pacific Rise (EPR, cruise MGL0812). Modeling indicates that the mid-crustal seismic reflection reflections are unlikely to arise from peg-leg multiples of the AML reflections, P-to-S converted phases, or scattering due to rough topography, but could probably arise from deeper multiple magma sills. Our results support the identification of Marjanović et al. (Nat Geosci 7(11):825-829, 2014) that a multi-level complex of melt lenses is present beneath the axis of the EPR.
Modeling digital pulse waveforms by solving one-dimensional Navier-stokes equations.
Fedotov, Aleksandr A; Akulova, Anna S; Akulov, Sergey A
2016-08-01
Mathematical modeling for composition distal arterial pulse wave in the blood vessels of the upper limbs was considered. Formation of distal arterial pulse wave is represented as a composition of forward and reflected pulse waves propagating along the arterial vessels. The formal analogy between pulse waves propagation along the human arterial system and the propagation of electrical oscillations in electrical transmission lines with distributed parameters was proposed. Dependencies of pulse wave propagation along the human arterial system were obtained by solving the one-dimensional Navier-Stokes equations for a few special cases.
Resolving Lithospheric Interfaces Using SS Waveform Stacks
NASA Astrophysics Data System (ADS)
Rychert, C. A.; Shearer, P. M.
2009-12-01
We image lithospheric interfaces globally using variations in the character of SS waveform stacks. The variations are caused by reflected phases, i.e., underside reflections (SS precursors) and topside multiples (SS reverberations), created at discontinuities near the midpoint of the SS raypath. Stacks from continental versus oceanic bouncepoint regions produce distinctly different SS waveforms, consistent with the large continent/ocean difference in crustal thickness. This difference can also be seen in data binned in bouncepoint caps with 10° radii. We develop a method to invert for the depth of lithospheric discontinuities using a modeling technique in which a reference waveform is convolved with a crustal operator. We demonstrate the utility of this method by inverting for Moho depth beneath Asia, where continental bouncepoint coverage is highest. The results from our method are correlated (correlation coefficient 0.8) with the CRUST 2.0 values averaged over sample bins of 10° radius. Beneath oceans, crustal depths are too shallow to be resolved by this method. However, SS stacks from regions in the Pacific where bouncepoint coverage is highest suggest the presence of a deeper velocity decrease with depth, which may be related to the lithosphere-asthenosphere boundary. Inversions for the depth of the interface indicate that it is centered at 15 - 170 km depth beneath the best-resolved bins. The character of the discontinuity varies systematically, increasing in depth from the East Pacific Rise towards older oceanic lithosphere. This imaging method has broad lateral resolution in comparison to receiver functions, but has the potential to sample lithospheric interfaces in regions where station coverage may be sparse.
NASA Astrophysics Data System (ADS)
Bigelow, Timothy A.; O'Brien, William D.
2005-08-01
Accurate estimates of the ultrasound pressure and/or intensity incident on the developing fetus on a patient-specific basis could improve the diagnostic potential of medical ultrasound by allowing the clinician to increase the transmit power while still avoiding the potential for harmful bioeffects. Neglecting nonlinear effects, the pressure/intensity can be estimated if an accurate estimate of the attenuation along the propagation path (i.e., total attenuation) can be obtained. Herein, a method for determining the total attenuation from the backscattered power spectrum from the developing fetus is proposed. The boundaries between amnion and either the fetus' skull or soft tissue are each modeled as planar impedance boundaries at an unknown orientation with respect to the sound beam. A mathematical analysis demonstrates that the normalized returned voltage spectrum from this model is independent of the planes orientation. Hence, the total attenuation can be estimated by comparing the location of the spectral peak in the reflection from the fetus to the location of the spectral peak in a reflection obtained from a rigid plane in a water bath. The independence of the attenuation estimate and plane orientation is then demonstrated experimentally using a Plexiglas plate, a rat's skull, and a tissue-mimicking phantom.
Full Waveform 3D Synthetic Seismic Algorithm for 1D Layered Anelastic Models
NASA Astrophysics Data System (ADS)
Schwaiger, H. F.; Aldridge, D. F.; Haney, M. M.
2007-12-01
Numerical calculation of synthetic seismograms for 1D layered earth models remains a significant aspect of amplitude-offset investigations, surface wave studies, microseismic event location approaches, and reflection interpretation or inversion processes. Compared to 3D finite-difference algorithms, memory demand and execution time are greatly reduced, enabling rapid generation of seismic data within workstation or laptop computational environments. We have developed a frequency-wavenumber forward modeling algorithm adapted to realistic 1D geologic media, for the purpose of calculating seismograms accurately and efficiently. The earth model consists of N layers bounded by two halfspaces. Each layer/halfspace is a homogeneous and isotropic anelastic (attenuative and dispersive) solid, characterized by a rectangular relaxation spectrum of absorption mechanisms. Compressional and shear phase speeds and quality factors are specified at a particular reference frequency. Solution methodology involves 3D Fourier transforming the three coupled, second- order, integro-differential equations for particle displacements to the frequency-horizontal wavenumber domain. An analytic solution of the resulting ordinary differential system is obtained. Imposition of welded interface conditions (continuity of displacement and stress) at all interfaces, as well as radiation conditions in the two halfspaces, yields a system of 6(N+1) linear algebraic equations for the coefficients in the ODE solution. An optimized inverse 2D Fourier transform to the space domain gives the seismic wavefield on a horizontal plane. Finally, three-component seismograms are obtained by accumulating frequency spectra at designated receiver positions on this plane, followed by a 1D inverse FFT from angular frequency ω to time. Stress-free conditions may be applied at the top or bottom interfaces, and seismic waves are initiated by force or moment density sources. Examples reveal that including attenuation
Automatic detection of echolocation clicks based on a Gabor model of their waveform.
Madhusudhana, Shyam; Gavrilov, Alexander; Erbe, Christine
2015-06-01
Prior research has shown that echolocation clicks of several species of terrestrial and marine fauna can be modelled as Gabor-like functions. Here, a system is proposed for the automatic detection of a variety of such signals. By means of mathematical formulation, it is shown that the output of the Teager-Kaiser Energy Operator (TKEO) applied to Gabor-like signals can be approximated by a Gaussian function. Based on the inferences, a detection algorithm involving the post-processing of the TKEO outputs is presented. The ratio of the outputs of two moving-average filters, a Gaussian and a rectangular filter, is shown to be an effective detection parameter. Detector performance is assessed using synthetic and real (taken from MobySound database) recordings. The detection method is shown to work readily with a variety of echolocation clicks and in various recording scenarios. The system exhibits low computational complexity and operates several times faster than real-time. Performance comparisons are made to other publicly available detectors including pamguard.
NASA Technical Reports Server (NTRS)
Taasan, Shlomo; Zhang, Hong
1993-01-01
Waveform multigrid method is an efficient method for solving certain classes of time dependent PDEs. This paper studies the relationship between this method and the analogous multigrid method for steady-state problems. Using a Fourier-Laplace analysis, practical convergence rate estimates of the waveform multigrid iterations are obtained. Experimental results show that the analysis yields accurate performance prediction.
NASA Astrophysics Data System (ADS)
Drilleau, M.; Dubois, A.; Blanchette-Guertin, J. F.; Kawamura, T.; Lognonne, P. H.
2015-12-01
In 2016, the InSight mission will provide the very first seismic records from Mars after installing a seismometer on the surface of the Red Planet. Obtaining information on the deep 1-D seismic structure of Mars using a single geophysical station will be challenging. However, successful test inversions using body and surface waves have been presented in a preliminary study by Panning et al. (2015). Future investigations need now to focus on inversions making a complete use of the seismic waveform. An important challenge is to investigate the effects of 3-D lateral variations of seismic velocity structures on seismograms. The HOPT (Higher Order Perturbation Theory) code originally developed by P. Lognonné and E. Clévédé (Lognonné, 1991 ; Lognonné and Clévédé, 2002) and based on the perturbation theory allows for the computation of synthetic seismograms in a 3-D Earth. We adapted the code for Mars and computed surface wave synthetics in a 3-D planet, initially only considering the effects of the planet's ellipticity as well as the lateral variations in the depth of the Moho which are known through gravity measurements (e.g. Neumann et al., 2004). Additional constraints from lateral variations in topography will be the focus of future work. These synthetics can be compared to future seismic data in order to identify a suite of Martian internal structure models that best match the data. To do so, we first need to estimate the resolvable parameters concerning the Mars deep interior while considering the 3-D effects, which is the main goal of this study. Furthermore, in preparation for the InSight mission data return phase, the computation of these synthetic (but realistic) seismograms is primordial to test the softwares developed by the InSight Mars Quake and Mars Structure Services (in charge of locating the seismic events, and using them to assess the internal structure of Mars).
Modeling regional wind erosion using different model
NASA Astrophysics Data System (ADS)
Guo, Zhongling; Chang, Chunping; Wang, Rende; Li, Jifeng; Li, Qing
2017-04-01
Wind erosion is an important factor causing soil degradation in arid and semi-arid regions. The need to quantitatively evaluate wind induced soil erosion yields many wind erosion models. These models include Wind Erosion Equation (WEQ), Revised Wind Erosion Equation (RWEQ),Wind Erosion Predicted System (WEPS) etc. at a field scale and Wind Erosion Assessment Model (WEAM), Integrated Wind Erosion Modeling System (IWEMS), AUStralian Land Erodibility Model (AUSLEM) etc. at a regional scale. The challenge of precisely estimating wind erosion at a regional scale still remain to date. To assess regional wind erosion, WEQ, RWEQ and WEPS have been scaled up to regional versions. However, no attempt is performed to compare these models for regional wind erosion modeling. In this study, the regional versions of WEQ, RWEQ, WEPS and WEAM, IWEMS, AUSLEM will be selected to model regional wind erosion of farmlands in the Kangbao County of northern China with annual soil loss by wind erosion based on 137 Cs analysis. Remote sensing image is used to determine the size and shape of local farmlands. Weather data of 2000-2010, China Soil Survey and published soil data, crops rotations etc. are compiled to generate raster layers of inputs for selected models using ArcGIS 10.2. These models were rebuilt based on ArcGIS Model-builder Module. Spatial distribution of annual soil loss by wind erosion determined from different model will be tested using annual soil loss data by 137 Cs analysis. Performances of these models will be investigated, and restrictions of these models will be further ascertained.
NASA Technical Reports Server (NTRS)
Quirk, Kevin J.; Srinivasan, Meera
2012-01-01
The minimum-shift-keying (MSK) radar waveform is formed by periodically extending a waveform that separately modulates the in-phase and quadrature- phase components of the carrier with offset pulse-shaped pseudo noise (PN) sequences. To generate this waveform, a pair of periodic PN sequences is each passed through a pulse-shaping filter with a half sinusoid impulse response. These shaped PN waveforms are then offset by half a chip time and are separately modulated on the in-phase and quadrature phase components of an RF carrier. This new radar waveform allows an increase in radar resolution without the need for additional spectrum. In addition, it provides self-interference suppression and configurable peak sidelobes. Compared strictly on the basis of the expressions for delay resolution, main-lobe bandwidth, effective Doppler bandwidth, and peak ambiguity sidelobe, it appears that bi-phase coded (BPC) outperforms the new MSK waveform. However, a radar waveform must meet certain constraints imposed by the transmission and reception of the modulation, as well as criteria dictated by the observation. In particular, the phase discontinuity of the BPC waveform presents a significant impediment to the achievement of finer resolutions in radar measurements a limitation that is overcome by using the continuous phase MSK waveform. The phase continuity, and the lower fractional out-of-band power of MSK, increases the allowable bandwidth compared with BPC, resulting in a factor of two increase in the range resolution of the radar. The MSK waveform also has been demonstrated to have an ambiguity sidelobe structure very similar to BPC, where the sidelobe levels can be decreased by increasing the length of the m-sequence used in its generation. This ability to set the peak sidelobe level is advantageous as it allows the system to be configured to a variety of targets, including those with a larger dynamic range. Other conventionally used waveforms that possess an even greater
Analysis and Application of LIDAR Waveform Data Using a Progressive Waveform Decomposition Method
NASA Astrophysics Data System (ADS)
Zhu, J.; Zhang, Z.; Hu, X.; Li, Z.
2011-09-01
Due to rich information of a full waveform of airborne LiDAR (light detection and ranging) data, the analysis of full waveform has been an active area in LiDAR application. It is possible to digitally sample and store the entire reflected waveform of small-footprint instead of only discrete point clouds. Decomposition of waveform data, a key step in waveform data analysis, can be categorized to two typical methods: 1) the Gaussian modelling method such as the Non-linear least-squares (NLS) algorithm and the maximum likelihood estimation using the Exception Maximization (EM) algorithm. 2) pulse detection method—Average Square Difference Function (ASDF). However, the Gaussian modelling methods strongly rely on initial parameters, whereas the ASDF omits the importance of parameter information of the waveform. In this paper, we proposed a fast algorithm—Progressive Waveform Decomposition (PWD) method to extract local maxims and fit the echo with Gaussian function, and calculate other parameters from the raw waveform data. On the one hand, experiments are implemented to evaluate the PWD method and the results demonstrate its robustness and efficiency. On the other hand, with the PWD parametric analysis of the full-waveform instead of a 3D point cloud, some special applications are investigated afterward.
JTRS/SCA and Custom/SDR Waveform Comparison
NASA Technical Reports Server (NTRS)
Oldham, Daniel R.; Scardelletti, Maximilian C.
2007-01-01
This paper compares two waveform implementations generating the same RF signal using the same SDR development system. Both waveforms implement a satellite modem using QPSK modulation at 1M BPS data rates with one half rate convolutional encoding. Both waveforms are partitioned the same across the general purpose processor (GPP) and the field programmable gate array (FPGA). Both waveforms implement the same equivalent set of radio functions on the GPP and FPGA. The GPP implements the majority of the radio functions and the FPGA implements the final digital RF modulator stage. One waveform is implemented directly on the SDR development system and the second waveform is implemented using the JTRS/SCA model. This paper contrasts the amount of resources to implement both waveforms and demonstrates the importance of waveform partitioning across the SDR development system.
Seismic waveform analyses for the 1938 Off Fukushima earthquake sequence
NASA Astrophysics Data System (ADS)
Murotani, S.; Satake, K.
2016-12-01
The 1938 Off Fukushima (Shioya-oki) earthquakes sequence, which consists of five earthquakes of Mjmaranging from 6.9 to 7.5, occurred in the southern part of the 2011 Tohoku earthquake source area. In this region, the 1938 sequence was the only known M 7 earthquakes until the 2011 Tohoku earthquake occurred. Abe (1977, Tectonophysics) estimated the focal mechanisms and seismic moments of these events. The source parameters of the earthquake sequence are shown in the following table. However, the slip distributions are not known. Murotani et al. (2004, SSJ Fall Meeting) estimated slip distributions for event 1 (Mw 7.6, Fault size 60 km x 70 km), event 2 (Mw 7.9, Fault size 80 km x 60 km), and event 3 (Mw 7.8, Fault size 90 km x 60 km) from inversion of near-field seismic waveforms at Sendai, Niigata, Maebashi, Mito, and Hongo (Tokyo). We compared the observed teleseismic waveforms at Christchurch (CHR), De Bilt (DBN), Pasadena (PAS), and Pulkovo (PUL) with the calculated waveforms from these slip distributions. The result showed that the computed waveforms fairly reproduced the phases of the observation but the amplitudes for all events were several to several tens of times larger than the observations. It means that the slip amount and Mwobtained from the near field seismic waveforms inversion were over-estimated. For event 3, the slip distribution estimated from near-field data has two large slip areas (asperities) to the north and south of the hypocenter, although only the southern asperity was able to reproduce the observed near-field seismic waveforms. When we calculate the teleseismic waveforms using one asperity model, the amplitudes become small and the phases are reproduced better compared to two asperities model. Event 3 therefore seemed to have only one asperity. In addition to the re-analysis of near field seismic data, tsunami waveforms will be also computed and compared with the observations. This study was supported by JSPS KAKENHI Grant Number JP16H
NASA Astrophysics Data System (ADS)
Bentham, H. L. M.; Morgan, J. V.; Angus, D. A.
2016-12-01
The UK has a large volume of high level and intermediate level radioactive waste and government policy is to dispose of this waste in a Geological Disposal Facility (GDF). This will be a highly-engineered facility capable of isolating radioactive waste within multiple protective barriers, deep underground, to ensure that no harmful quantities of radioactivity ever reach the surface environment. Although no specific GDF site in the UK has been chosen, granite is one of the candidate host rocks due to its strength, in engineering terms, and because of its low permeability in consideration of groundwater movement. We design time-lapse seismic surveys to characterise geological models of naturally fractured granite with GDF-related tunnel damage zones at a potential disposal depth of 1000 m (the UK GDF might be shallower). Additionally, we use effective medium models to calculate the velocity change when the fracture density is increased in the damage zones, and find a reduction of 60 m/s in P-wave velocity when the fracture density is doubled. Next, we simulate seismic surveys and apply 3D Full Waveform Inversion (FWI) to see how well we can recover the low-velocity damage zones. Furthermore we evaluate the effectiveness of using a survey design consisting of surface and tunnel receivers (a combined array) to resolve the target. After applying FWI we find the velocity anomaly within the damage zone can be resolved to within 2 m/s (3%) and the shape of the damage zone is resolved to 12.5 m (within a single grid cell). Using the combined array we are able to resolve the anomaly strength and shape more completely. When we add further complexity to the model by including tunnel infrastructure, we conclude the combined array is essential in recovering the tunnel damage zone. Our findings show that it is beneficial to use 3D FWI and novel survey designs for characterising subtle variations as may be present in granite, information that could assist in the GDF site selection
NASA Astrophysics Data System (ADS)
Uebbing, Bernd; Roscher, Ribana; Kusche, Jürgen
2016-04-01
Satellite radar altimeters allow global monitoring of mean sea level changes over the last two decades. However, coastal regions are less well observed due to influences on the returned signal energy by land located inside the altimeter footprint. The altimeter emits a radar pulse, which is reflected at the nadir-surface and measures the two-way travel time, as well as the returned energy as a function of time, resulting in a return waveform. Over the open ocean the waveform shape corresponds to a theoretical model which can be used to infer information on range corrections, significant wave height or wind speed. However, in coastal areas the shape of the waveform is significantly influenced by return signals from land, located in the altimeter footprint, leading to peaks which tend to bias the estimated parameters. Recently, several approaches dealing with this problem have been published, including utilizing only parts of the waveform (sub-waveforms), estimating the parameters in two steps or estimating additional peak parameters. We present a new approach in estimating sub-waveforms using conditional random fields (CRF) based on spatio-temporal waveform information. The CRF piece-wise approximates the measured waveforms based on a pre-derived dictionary of theoretical waveforms for various combinations of the geophysical parameters; neighboring range gates are likely to be assigned to the same underlying sub-waveform model. Depending on the choice of hyperparameters in the CRF estimation, the classification into sub-waveforms can either be more fine or coarse resulting in multiple sub-waveform hypotheses. After the sub-waveforms have been detected, existing retracking algorithms can be applied to derive water heights or other desired geophysical parameters from particular sub-waveforms. To identify the optimal heights from the multiple hypotheses, instead of utilizing a known reference height, we apply a Dijkstra-algorithm to find the "shortest path" of all
Seismic Structure of Southeast Asia from Full Waveform Seismic Ambient Noise Tomography
NASA Astrophysics Data System (ADS)
Cummins, P. R.; Saygin, E.; Fichtner, A.; Masturyono, M.
2015-12-01
We image the lower crust and upper-mantle structure of Southeast Asia with a 3D full waveform adjoint inversion scheme by directly inverting Green's functions retrieved from interstation seismic noise correlations. Synthetic Green's functions are computed at a period range between 10 and 40 s to simulate the wave propagation in the region. Misfits between observed and synthetic waveforms are reduced by iteratively updating model parameters using sensitivity kernels with a conjugate-gradient optimization method. The final model is verified via comparing the simulated waveforms with the recorded earthquakes in the region. The balanced coverage of rays in the region enabled us to image complex structure. The Australian plate is characterized with higher velocities for most of the crust, where most of Indonesia, and its surroundings show complex structure with low velocities. The transition from the oceanic part of the Australian Plate to the continental crust adjacent to the Banda Arc is clearly imaged.
Refined Local and Regional Seismic Velocity and Attenuation Models from Finite-Frequency Waveforms
2008-09-30
the velocities and quality factors of P and S waves specified on a l°xl ° horizontal grid and at 24 depths from 0 to 660 km. Figure 3 shows a few map...Technologies VPHf*"d VPh 0,a Xbr. dgo,u am 42SO 404 30 30 MW 3500 go am a’-s 42 5000 2 40 44o55 s50 0 45 s 6 o 4 35 4500 40 400 24 39 42 rNO 34400 am St
2.5D real waveform and real noise simulation of receiver functions in 3D models
NASA Astrophysics Data System (ADS)
Schiffer, Christian; Jacobsen, Bo; Balling, Niels
2014-05-01
There are several reasons why a real-data receiver function differs from the theoretical receiver function in a 1D model representing the stratification under the seismometer. Main reasons are ambient noise, spectral deficiencies in the impinging P-waveform, and wavefield propagation in laterally varying velocity variations. We present a rapid "2.5D" modelling approach which takes these aspects into account, so that a given 3D velocity model of the crust and uppermost mantle can be tested more realistically against observed recordings from seismometer arrays. Each recorded event at each seismometer is simulated individually through the following steps: A 2D section is extracted from the 3D model along the direction towards the hypocentre. A properly slanted plane or curved impulsive wavefront is propagated through this 2D section, resulting in noise free and spectrally complete synthetic seismometer data. The real vertical component signal is taken as a proxy of the real impingent wavefield, so by convolution and subsequent addition of real ambient noise recorded just before the P-arrival we get synthetic vertical and horizontal component data which very closely match the spectral signal content and signal to noise ratio of this specific recording. When these realistic synthetic data undergo exactly the same receiver function estimation and subsequent graphical display we get a much more realistic image to compare to the real-data receiver functions. We applied this approach to the Central Fjord area in East Greenland (Schiffer et al., 2013), where a 3D velocity model of crust and uppermost mantle was adjusted to receiver functions from 2 years of seismometer recordings and wide angle crustal profiles (Schlindwein and Jokat, 1999; Voss and Jokat, 2007). Computationally this substitutes tens or hundreds of heavy 3D computations with hundreds or thousands of single-core 2D computations which parallelize very efficiently on common multicore systems. In perspective
ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS
Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.
2008-10-17
This quarter, we have focused on several tasks: (1) Building a high-quality catalog of earthquake source parameters for the Middle East and East Asia. In East Asia, we computed source parameters using the CAP method for a set of events studied by Herrman et al., (MRR, 2006) using a complete waveform technique. Results indicated excellent agreement with the moment magnitudes in the range 3.5 -5.5. Below magnitude 3.5 the scatter increases. For events with more than 2-3 observations at different azimuths, we found good agreement of focal mechanisms. Depths were generally consistent, although differences of up to 10 km were found. These results suggest that CAP modeling provides estimates of source parameters at least as reliable as complete waveform modeling techniques. However, East Asia and the Yellow Sea Korean Paraplatform (YSKP) region studied are relatively laterally homogeneous and may not benefit from the CAP method’s flexibility to shift waveform segments to account for path-dependent model errors. A more challenging region to study is the Middle East where strong variations in sedimentary basin, crustal thickness and crustal and mantle seismic velocities greatly impact regional wave propagation. We applied the CAP method to a set of events in and around Iran and found good agreement between estimated focal mechanisms and those reported by the Global Centroid Moment Tensor (CMT) catalog. We found a possible bias in the moment magnitudes that may be due to the thick low-velocity crust in the Iranian Plateau. (2) Testing Methods on a Lifetime Regional Data Set. In particular, the recent 2/21/08 Nevada Event and Aftershock Sequence occurred in the middle of USArray, producing over a thousand records per event. The tectonic setting is quite similar to Central Iran and thus provides an excellent testbed for CAP+ at ranges out to 10°, including extensive observations of crustal thinning and thickening and various Pnl complexities. Broadband modeling in 1D, 2D
2007-07-13
northwest. 2 Figure 1. Relocated earthquakes in the Yunnan (red dots) and Sichuan (black dots) region from this study. White and green...Because of the high seismicity (more than 1000 earthquakes with magnitudes greater than 2.5 per year) and severe earthquake hazards, the Sichuan and...cross-sections of Vs model at latitudes of 27o, 26o and 25oN. 28 7. Earthquake locations and 3D velocity models in the Sichuan region For the
Waveform Inversion of the Teleseismic Wavefield
NASA Astrophysics Data System (ADS)
He, Y.; Levander, A.; Niu, F.
2006-12-01
The issue of seismic inversion/imaging can be generalized to find the velocity perturbation field that provides the best explanation for seismic data. Theoretically, migration is the first iteration in the inversion process, not the solution that minimizes the RMS error between observed and model-predicted wavefield. Waveform inversion, however, seeks to find the true perturbation field by directly solving the partial differential wave equations. When the wavefield is densely sampled, waveform inversion has been proven to be able to image sub-wavelength scale structure. Recent developments in passive seismic observations make it possible to apply imaging techniques developed for petroleum exploration, such as waveform tomography, to investigate crustal and mantle structures. We have been attempting to apply this technique to the teleseismic wavefield. Here we start with the relative simple 2D SH-wave case with reflection source-receiver geometry to target the core-mantle boundary (CMB) region. Many studies suggest that the lowermost several hundreds of kilometers of Earth's mantle, the D" layer is complicated and heterogeneous in terms of seismic structure. D" heterogeneities cover a wide range of scales that vary from a few kilometers to a few thousands of kilometers laterally and tenths to tens of percents in intensity. The D" layer also has very different 1D velocity structure. Different techniques have been used to study these very different structures. It is thus very interesting to see whether we can use teleseismic S and ScS waveforms to image these heterogeneities. The partial differential SH wave equation is parameterized in the discrete frequency-space domain. Inversion is performed iteratively to minimize the misfit between observed and model-predicted waveforms using a local descent algorithm. Iteration is employed at discrete frequencies, moving from low to high to mitigate the nonlinearity of the problem. The teleseismic wavefield is approximated by a
Altimeter waveform software design
NASA Technical Reports Server (NTRS)
Hayne, G. S.; Miller, L. S.; Brown, G. S.
1977-01-01
Techniques are described for preprocessing raw return waveform data from the GEOS-3 radar altimeter. Topics discussed include: (1) general altimeter data preprocessing to be done at the GEOS-3 Data Processing Center to correct altimeter waveform data for temperature calibrations, to convert between engineering and final data units and to convert telemetered parameter quantities to more appropriate final data distribution values: (2) time "tagging" of altimeter return waveform data quantities to compensate for various delays, misalignments and calculational intervals; (3) data processing procedures for use in estimating spacecraft attitude from altimeter waveform sampling gates; and (4) feasibility of use of a ground-based reflector or transponder to obtain in-flight calibration information on GEOS-3 altimeter performance.
Esper, Stephen A; Pinsky, Michael R
2014-12-01
The bedside measurement of continuous arterial pressure values from waveform analysis has been routinely available via indwelling arterial catheterization for >50 years. Invasive blood pressure monitoring has been utilized in critically ill patients, in both the operating room and critical care units, to facilitate rapid diagnoses of cardiovascular insufficiency and monitor response to treatments aimed at correcting abnormalities before the consequences of either hypo- or hypertension are seen. Minimally invasive techniques to estimate cardiac output (CO) have gained increased appeal. This has led to the increased interest in arterial waveform analysis to provide this important information, as it is measured continuously in many operating rooms and intensive care units. Arterial waveform analysis also allows for the calculation of many so-called derived parameters intrinsically created by this pulse pressure profile. These include estimates of left ventricular stroke volume (SV), CO, vascular resistance, and during positive-pressure breathing, SV variation, and pulse pressure variation. This article focuses on the principles of arterial waveform analysis and their determinants, components of the arterial system, and arterial pulse contour. It will also address the advantage of measuring real-time CO by the arterial waveform and the benefits to measuring SV variation. Arterial waveform analysis has gained a large interest in the overall assessment and management of the critically ill and those at a risk of hemodynamic deterioration.
NASA Astrophysics Data System (ADS)
Griffin, Maurice; Sugawara, Glen
1995-02-01
A system for storing an arbitrary waveform on nonvolatile random access memory (NVRAM) device and generating an analog signal using the NVRAM device is described. A central processing unit is used to synthesize an arbitrary waveform and create a digital representation of the waveform and transfer the digital representation to a microprocessor which, in turn, writes the digital data into an NVRAM device which has been mapped into a portion of the microprocessor address space. The NVRAM device is removed from address space and placed into an independent waveform generation unit. In the waveform generation unit, an address clock provides an address timing signal and a cycle clock provides a transmit signal. Both signals are applied to an address generator. When both signals are present, the address generator generates and transmits to the NVRAM device a new address for each cycle of the address timing signal. In response to each new address generated, the NVRAM devices provides a digital output which is applied to a digital to analog converter. The converter produces a continuous analog output which is smoothed by a filter to produce the arbitrary waveform.
2012-04-20
Indian tectonic plates . Without knowing the true lateral changes in anisotropy and including large continental provinces within the model it is...between recordings of seismic waves traversing the region from Tibet to the Red Sea compared to synthetics from the current iteration model is the...also significantly increase anomaly strength while sharpening the anomaly edges to create stronger and more pronounced tectonic structures. The
Low frequency AC waveform generator
Bilharz, Oscar W.
1986-01-01
Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.
NASA Astrophysics Data System (ADS)
Adamczyk, A.; Malinowski, M.; Malehmir, A.
2014-06-01
Full-waveform inversion (FWI) is an iterative optimization technique that provides high-resolution models of subsurface properties. Frequency-domain, acoustic FWI was applied to seismic data acquired over a known quick-clay landslide scar in southwest Sweden. We inverted data from three 2-D seismic profiles, 261-572 m long, two of them shot with small charges of dynamite and one with a sledgehammer. To our best knowledge this is the first published application of FWI to sledgehammer data. Both sources provided data suitable for waveform inversion, the sledgehammer data containing even wider frequency spectrum. Inversion was performed for frequency groups between 27.5 and 43.1 Hz for the explosive data and 27.5-51.0 Hz for the sledgehammer. The lowest inverted frequency was limited by the resonance frequency of the standard 28-Hz geophones used in the survey. High-velocity granitic bedrock in the area is undulated and very shallow (15-100 m below the surface), and exhibits a large P-wave velocity contrast to the overlying normally consolidated sediments. In order to mitigate the non-linearity of the inverse problem we designed a multiscale layer-stripping inversion strategy. Obtained P-wave velocity models allowed to delineate the top of the bedrock and revealed distinct layers within the overlying sediments of clays and coarse-grained materials. Models were verified in an extensive set of validating procedures and used for pre-stack depth migration, which confirmed their robustness.
Genetic algorithm reveals energy-efficient waveforms for neural stimulation.
Wongsarnpigoon, Amorn; Grill, Warren M
2009-01-01
Energy consumption is an important consideration for battery-powered implantable stimulators. We used a genetic algorithm (GA) that mimics biological evolution to determine the energy-optimal waveform shape for neural stimulation. The GA was coupled to NEURON using a model of extracellular stimulation of a mammalian myelinated axon. Stimulation waveforms represented the organisms of a population, and each waveform's shape was encoded into genes. The fitness of each waveform was based on its energy efficiency and ability to elicit an action potential. After each generation of the GA, waveforms mated to produce offspring waveforms, and a new population was formed consisting of the offspring and the fittest waveforms of the previous generation. Over the course of the GA, waveforms became increasingly energy-efficient and converged upon a highly energy-efficient shape. The resulting waveforms resembled truncated normal curves or sinusoids and were 3-74% more energy-efficient than several waveform shapes commonly used in neural stimulation. If implemented in implantable neural stimulators, the GA optimized waveforms could prolong battery life, thereby reducing the costs and risks of battery-replacement surgery.
2009-09-30
Earth model, Phvs. Earth Planet Int. 25: 297-356. Kikuchi, M. and H. Kanamori (1982). Inversion of complex body waves, Bull. Seism . Soc. Am. 72: 491...California, Bull. Seism . Soc. Am. 94: 1748-1761. Maggi, A., C. Tape, M. Chen, D. Chao, and J. Tromp (2009). An Automated time-window selection algorithm...Zhao, L. S. and D. V. Helmberger (1994). Source estimation from broadband regional seismograms, Bull. Seism . Soc.Am. 84:91-104. 200
Hybrid regional air pollution models
Drake, R.L.
1980-03-01
This discussion deals with a family of air quality models for predicting and analyzing the fine particulate loading in the atmosphere, for assessing the extent and degree of visibility impairment, and for determining the potential of pollutants for increasing the acidity of soils and water. The major horizontal scales of interest are from 400km to 2000km; and the time scales may vary from several hours, to days, weeks, and a few months or years, depending on the EPA regulations being addressed. First the role air quality models play in the general family of atmospheric simulation models is described. Then, the characteristics of a well-designed, comprehensive air quality model are discussed. Following this, the specific objectives of this workshop are outlined, and their modeling implications are summarized. There are significant modeling differences produced by the choice of the coordinate system, whether it be the fixed Eulerian system, the moving Lagrangian system, or some hybrid of the two. These three systems are briefly discussed, and a list of hybrid models that are currently in use are given. Finally, the PNL regional transport model is outlined and a number of research needs are listed.
Do regional climate models represent regional climate?
NASA Astrophysics Data System (ADS)
Maraun, Douglas; Widmann, Martin
2014-05-01
When using climate change scenarios - either from global climate models or further downscaled - to assess localised real world impacts, one has to ensure that the local simulation indeed correctly represents the real world local climate. Representativeness has so far mainly been discussed as a scale issue: simulated meteorological variables in general represent grid box averages, whereas real weather is often expressed by means of point values. As a result, in particular simulated extreme values are not directly comparable with observed local extreme values. Here we argue that the issue of representativeness is more general. To illustrate this point, assume the following situations: first, the (GCM or RCM) simulated large scale weather, e.g., the mid-latitude storm track, might be systematically distorted compared to observed weather. If such a distortion at the synoptic scale is strong, the simulated local climate might be completely different from the observed. Second, the orography even of high resolution RCMs is only a coarse model of true orography. In particular in mountain ranges the simulated mesoscale flow might therefore considerably deviate from the observed flow, leading to systematically displaced local weather. In both cases, the simulated local climate does not represent observed local climate. Thus, representativeness also encompasses representing a particular location. We propose to measure this aspect of representativeness for RCMs driven with perfect boundary conditions as the correlation between observations and simulations at the inter-annual scale. In doing so, random variability generated by the RCMs is largely averaged out. As an example, we assess how well KNMIs RACMO2 RCM at 25km horizontal resolution represents winter precipitation in the gridded E-OBS data set over the European domain. At a chosen grid box, RCM precipitation might not be representative of observed precipitation, in particular in the rain shadow of major moutain ranges
Compressive full waveform lidar
NASA Astrophysics Data System (ADS)
Yang, Weiyi; Ke, Jun
2017-05-01
To avoid high bandwidth detector, fast speed A/D converter, and large size memory disk, a compressive full waveform LIDAR system, which uses a temporally modulated laser instead of a pulsed laser, is studied in this paper. Full waveform data from NEON (National Ecological Observatory Network) are used. Random binary patterns are used to modulate the source. To achieve 0.15 m ranging resolution, a 100 MSPS A/D converter is assumed to make measurements. SPIRAL algorithm with canonical basis is employed when Poisson noise is considered in the low illuminated condition.
Investigating the Relationship Between Waveform Correlation and Seismic Source Mechanisms
NASA Astrophysics Data System (ADS)
Scales, M. M.; Baker, G. E.; Slinkard, M.
2016-12-01
A common practice in nuclear monitoring is to use waveform correlation as a method of event detection. Earthquake waveforms, for example, are correlated with seismic data to detect other similar earthquakes. Likewise, explosion waveforms are used to identify other explosions from the same area. However, for monitoring purposes high confidence in the identification of source type is important. A high correlation coefficient does not necessarily guarantee that the template event and a new detected event are of the same source type. For example, an explosion waveform could correlate well with an earthquake template if much of the waveform's characteristics are due to propagation effects. Here, we investigate what we can confidently infer about source type from waveform correlations by correlating seismograms of earthquakes from the Geysers Geothermal Field. There are 53 earthquakes from this region with full moment tensor solutions, which range from 80% double couple to 66% isotropic to 75% CLVD (Boyd, et al. 2015). We cross-correlate the P and S waveforms using all 3 components for three filter bands (1-4Hz, 0.1-2Hz, 0.3-1Hz) and then cluster the waveforms based on their cross-correlation coefficients to see whether similar waveforms also have similar source mechanisms. We also decompose the waveforms into their subspaces using singular value decomposition to look for physical meaning in their basis functions.
Simulating Full-Waveform LIDAR
2009-09-01
within the waveform signal. These peaks correspond to object reflections, and are used to generate a 3D point cloud. Figure 1. Inputs and outputs to...day = strmid(temp, 8,2) date = strtrim(day)+month+’Lidar_model_output’ print , ’Date:’, date hit_map_file = outdir + ’hit_map_’+date+’.dat...model_sample_rate = 1./time_step_ns aperture_diam_pix = aperture_diam_m*100.*(1./cm_per_pixel) print , ’Time step (ns):’, time_step_ns print , ’Distance (cm
Georgia tech catalog of gravitational waveforms
NASA Astrophysics Data System (ADS)
Jani, Karan; Healy, James; Clark, James A.; London, Lionel; Laguna, Pablo; Shoemaker, Deirdre
2016-10-01
This paper introduces a catalog of gravitational waveforms from the bank of simulations by the numerical relativity effort at Georgia Tech. Currently, the catalog consists of 452 distinct waveforms from more than 600 binary black hole simulations: 128 of the waveforms are from binaries with black hole spins aligned with the orbital angular momentum, and 324 are from precessing binary black hole systems. The waveforms from binaries with non-spinning black holes have mass-ratios q = m 1/m 2 ≤ 15, and those with precessing, spinning black holes have q ≤ 8. The waveforms expand a moderate number of orbits in the late inspiral, the burst during coalescence, and the ring-down of the final black hole. Examples of waveforms in the catalog matched against the widely used approximate models are presented. In addition, predictions of the mass and spin of the final black hole by phenomenological fits are tested against the results from the simulation bank. The role of the catalog in interpreting the GW150914 event and future massive binary black-hole search in LIGO is discussed. The Georgia Tech catalog is publicly available at einstein.gatech.edu/catalog.
NASA Astrophysics Data System (ADS)
Dai, Meng-Xue; Chen, Jing-Bo; Cao, Jian
2017-07-01
Full-waveform inversion (FWI) is an ill-posed optimization problem which is sensitive to noise and initial model. To alleviate the ill-posedness of the problem, regularization techniques are usually adopted. The ℓ1-norm penalty is a robust regularization method that preserves contrasts and edges. The Orthant-Wise Limited-Memory Quasi-Newton (OWL-QN) method extends the widely-used limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) method to the ℓ1-regularized optimization problems and inherits the efficiency of L-BFGS. To take advantage of the ℓ1-regularized method and the prior model information obtained from sonic logs and geological information, we implement OWL-QN algorithm in ℓ1-regularized FWI with prior model information in this paper. Numerical experiments show that this method not only improve the inversion results but also has a strong anti-noise ability.
NASA Astrophysics Data System (ADS)
Salas, R. A.; Pleite, J.
2010-05-01
This paper presents a new dynamic model of equivalent circuit to simulate in the time-domain the effects of saturation and power losses in a nonlinear magnetic component. The parameters of the model are a nonlinear inductance and a nonlinear loss resistance that are computed via two-dimensional finite elements. The effectiveness of the model is analyzed in the case of a soft ferrite inductor excited by a sinusoidal voltage source at frequencies of 500 Hz and 40 kHz. The resulting voltage and current waveforms of the inductor taken in the laboratory are then compared with those computed via the PSIM circuit simulator. PSIM is a simulation software designed for power electronics, motor control, and dynamic system simulation.
NASA Astrophysics Data System (ADS)
Canitano, Alexandre; Hsu, Ya-Ju; Lee, Hsin-Ming; Linde, Alan T.; Sacks, Selwyn
2017-08-01
We propose an approach for calibrating the horizontal tidal shear components [(differential extension (γ _1 ) and engineering shear (γ _2 )] of two Sacks-Evertson (in Pap Meteorol Geophys 22:195-208, 1971) SES-3 borehole strainmeters installed in the Longitudinal Valley in eastern Taiwan. The method is based on the waveform reconstruction of the Earth and ocean tidal shear signals through linear regressions on strain gauge signals, with variable sensor azimuth. This method allows us to derive the orientation of the sensor without any initial constraints and to calibrate the shear strain components γ _1 and γ _2 against M_2 tidal constituent. The results illustrate the potential of tensor strainmeters for recording horizontal tidal shear strain.
Low frequency ac waveform generator
Bilharz, O.W.
1983-11-22
Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.
Waveform Design for Wireless Power Transfer
NASA Astrophysics Data System (ADS)
Clerckx, Bruno; Bayguzina, Ekaterina
2016-12-01
Far-field Wireless Power Transfer (WPT) has attracted significant attention in recent years. Despite the rapid progress, the emphasis of the research community in the last decade has remained largely concentrated on improving the design of energy harvester (so-called rectenna) and has left aside the effect of transmitter design. In this paper, we study the design of transmit waveform so as to enhance the DC power at the output of the rectenna. We derive a tractable model of the non-linearity of the rectenna and compare with a linear model conventionally used in the literature. We then use those models to design novel multisine waveforms that are adaptive to the channel state information (CSI). Interestingly, while the linear model favours narrowband transmission with all the power allocated to a single frequency, the non-linear model favours a power allocation over multiple frequencies. Through realistic simulations, waveforms designed based on the non-linear model are shown to provide significant gains (in terms of harvested DC power) over those designed based on the linear model and over non-adaptive waveforms. We also compute analytically the theoretical scaling laws of the harvested energy for various waveforms as a function of the number of sinewaves and transmit antennas. Those scaling laws highlight the benefits of CSI knowledge at the transmitter in WPT and of a WPT design based on a non-linear rectenna model over a linear model. Results also motivate the study of a promising architecture relying on large-scale multisine multi-antenna waveforms for WPT. As a final note, results stress the importance of modeling and accounting for the non-linearity of the rectenna in any system design involving wireless power.
Platform for Postprocessing Waveform-Based NDE
NASA Technical Reports Server (NTRS)
Roth, Don
2008-01-01
Taking advantage of the similarities that exist among all waveform-based non-destructive evaluation (NDE) methods, a common software platform has been developed containing multiple- signal and image-processing techniques for waveforms and images. The NASA NDE Signal and Image Processing software has been developed using the latest versions of LabVIEW, and its associated Advanced Signal Processing and Vision Toolkits. The software is useable on a PC with Windows XP and Windows Vista. The software has been designed with a commercial grade interface in which two main windows, Waveform Window and Image Window, are displayed if the user chooses a waveform file to display. Within these two main windows, most actions are chosen through logically conceived run-time menus. The Waveform Window has plots for both the raw time-domain waves and their frequency- domain transformations (fast Fourier transform and power spectral density). The Image Window shows the C-scan image formed from information of the time-domain waveform (such as peak amplitude) or its frequency-domain transformation at each scan location. The user also has the ability to open an image, or series of images, or a simple set of X-Y paired data set in text format. Each of the Waveform and Image Windows contains menus from which to perform many user actions. An option exists to use raw waves obtained directly from scan, or waves after deconvolution if system wave response is provided. Two types of deconvolution, time-based subtraction or inverse-filter, can be performed to arrive at a deconvolved wave set. Additionally, the menu on the Waveform Window allows preprocessing of waveforms prior to image formation, scaling and display of waveforms, formation of different types of images (including non-standard types such as velocity), gating of portions of waves prior to image formation, and several other miscellaneous and specialized operations. The menu available on the Image Window allows many further image
Finite-fault analysis of the 2004 Parkfield, California, earthquake using Pnl waveforms
Mendoza, C.; Hartzell, S.
2008-01-01
We apply a kinematic finite-fault inversion scheme to Pnl displacement waveforms recorded at 14 regional stations (Δ<2°) to recover the distribution of coseismic slip for the 2004 Parkfield earthquake using both synthetic Green’s functions (SGFs) calculated for one-dimensional (1D) crustal-velocity models and empirical Green’s functions (EGFs) based on the recordings of a single Mw 5.0 aftershock. Slip is modeled on a rectangular fault subdivided into 2×2 km subfaults assuming a constant rupture velocity and a 0.5 sec rise time. A passband filter of 0.1–0.5 Hz is applied to both data and subfault responses prior to waveform inversion. The SGF inversions are performed such that the final seismic moment is consistent with the known magnitude (Mw 6.0) of the earthquake. For these runs, it is difficult to reproduce the entire Pnl waveform due to inaccuracies in the assumed crustal structure. Also, the misfit between observed and predicted vertical waveforms is similar in character for different rupture velocities, indicating that neither the rupture velocity nor the exact position of slip sources along the fault can be uniquely identified. The pattern of coseismic slip, however, compares well with independent source models derived using other data types, indicating that the SGF inversion procedure provides a general first-order estimate of the 2004 Parkfield rupture using the vertical Pnl records. The best-constrained slip model is obtained using the single-aftershock EGF approach. In this case, the waveforms are very well reproduced for both vertical and horizontal components, suggesting that the method provides a powerful tool for estimating the distribution of coseismic slip using the regional Pnl waveforms. The inferred slip model shows a localized patch of high slip (55 cm peak) near the hypocenter and a larger slip area (~50 cm peak) extending between 6 and 20 km to the northwest.
Analog device simulates physiological waveforms
NASA Technical Reports Server (NTRS)
Hickman, D. M.
1964-01-01
An analog physiological simulator generates representative waveforms for a wide range of physiological conditions. Direct comparison of these waveforms with those from telemetric inputs permits quick detection of signal parameter degradation.
NASA Astrophysics Data System (ADS)
Toyokuni, G.; Takenaka, H.
2007-12-01
We propose a method to obtain effective grid parameters for the finite-difference (FD) method with standard Earth models using analytical ways. In spite of the broad use of the heterogeneous FD formulation for seismic waveform modeling, accurate treatment of material discontinuities inside the grid cells has been a serious problem for many years. One possible way to solve this problem is to introduce effective grid elastic moduli and densities (effective parameters) calculated by the volume harmonic averaging of elastic moduli and volume arithmetic averaging of density in grid cells. This scheme enables us to put a material discontinuity into an arbitrary position in the spatial grids. Most of the methods used for synthetic seismogram calculation today receives the blessing of the standard Earth models, such as the PREM, IASP91, SP6, and AK135, represented as functions of normalized radius. For the FD computation of seismic waveform with such models, we first need accurate treatment of material discontinuities in radius. This study provides a numerical scheme for analytical calculations of the effective parameters for an arbitrary spatial grids in radial direction as to these major four standard Earth models making the best use of their functional features. This scheme can analytically obtain the integral volume averages through partial fraction decompositions (PFDs) and integral formulae. We have developed a FORTRAN subroutine to perform the computations, which is opened to utilization in a large variety of FD schemes ranging from 1-D to 3-D, with conventional- and staggered-grids. In the presentation, we show some numerical examples displaying the accuracy of the FD synthetics simulated with the analytical effective parameters.
Genetic Algorithm Reveals Energy-Efficient Waveforms for Neural Stimulation
Wongsarnpigoon, Amorn; Grill, Warren M.
2013-01-01
Energy consumption is an important consideration for battery-powered implantable stimulators. We used a genetic algorithm (GA) that mimics biological evolution to determine the energy-optimal waveform shape for neural stimulation. The GA was coupled to NEURON using a model of extracellular stimulation of a mammalian myelinated axon. Stimulation waveforms represented the organisms of a population, and each waveform’s shape was encoded into genes. The fitness of each waveform was based on its energy efficiency and ability to elicit an action potential. After each generation of the GA, waveforms mated to produce offspring waveforms, and a new population was formed consisting of the offspring and the fittest waveforms of the previous generation. Over the course of the GA, waveforms became increasingly energy-efficient and converged upon a highly energy-efficient shape. The resulting waveforms resembled truncated normal curves or sinusoids and were 3–74% more energy-efficient than several waveform shapes commonly used in neural stimulation. If implemented in implantable neural stimulators, the GA optimized waveforms could prolong battery life, thereby reducing the costs and risks of battery-replacement surgery. PMID:19964233
NASA Astrophysics Data System (ADS)
Cesca, Simone; Heimann, Sebastian; Kriegerowski, Marius; Dahm, Torsten
2016-04-01
Regional and teleseismic full waveform moment tensor inversion are nowadays routinely performed to derive moment tensors for moderate to large earthquakes. The extension of moment tensor inversion to weak events and microseismicity is limited by low amplitude of seismic signals and noise contamination. Noise contaminated low frequency seismic signals are hardly usable, while high frequency seismic signals are difficult to model at larger distances, because they are affected by unresolved small scale velocity anomalies and the strong physical attenuation of amplitudes at high frequencies. Waveform matching and signal classification methods help to reveal similar rupture processes and increase the event detection rate. We discuss here a novel inversion approach, which combines waveform clustering method, waveform stacking procedures and full waveform moment tensor inversion to resolve moment tensors beyond the current lower magnitude treshold. The method applies to similar events, with similar locations and focal mechanisms, and provides a single moment tensor for a cluster of similar events. This condition is met upon the waveform correlation analysis at a reference station at close epicentral distance, which helps to recognise similar events, estimate interevent times and relative magnitudes. Through the stack of similar waveforms, we enhance the signal-to-noise ratio of full waveform signals, and are able to perform moment tensor inversion at larger distances and/or at lower frequencies. The performance of a low frequency full waveform moment tensor inversion on stacked, similar waveforms provides a stable moment tensor for the cluster of similar events. The resulting cumulative scalar moment can be used to infer the scalar moment of single events, taking advantage of the scaling of similar waveforms at the reference local station. We demonstrate the method using both synthetic and real data from the 2014/2015 collapse of the Bárðarbunga caldera, Iceland.
Hsieh, Chi-Hsuan; Chiu, Yu-Fang; Shen, Yi-Hsiang; Chu, Ta-Shun; Huang, Yuan-Hao
2016-02-01
This paper presents an ultra-wideband (UWB) impulse-radio radar signal processing platform used to analyze human respiratory features. Conventional radar systems used in human detection only analyze human respiration rates or the response of a target. However, additional respiratory signal information is available that has not been explored using radar detection. The authors previously proposed a modified raised cosine waveform (MRCW) respiration model and an iterative correlation search algorithm that could acquire additional respiratory features such as the inspiration and expiration speeds, respiration intensity, and respiration holding ratio. To realize real-time respiratory feature extraction by using the proposed UWB signal processing platform, this paper proposes a new four-segment linear waveform (FSLW) respiration model. This model offers a superior fit to the measured respiration signal compared with the MRCW model and decreases the computational complexity of feature extraction. In addition, an early-terminated iterative correlation search algorithm is presented, substantially decreasing the computational complexity and yielding negligible performance degradation. These extracted features can be considered the compressed signals used to decrease the amount of data storage required for use in long-term medical monitoring systems and can also be used in clinical diagnosis. The proposed respiratory feature extraction algorithm was designed and implemented using the proposed UWB radar signal processing platform including a radar front-end chip and an FPGA chip. The proposed radar system can detect human respiration rates at 0.1 to 1 Hz and facilitates the real-time analysis of the respiratory features of each respiration period.
Harmonic minimization waveforms for modulated heating experiments at HAARP
NASA Astrophysics Data System (ADS)
Jin, G.; Spasojevic, M.; Cohen, M. B.; Inan, U. S.
2012-11-01
Modulated High Frequency (few MHz) heating of the D-region ionosphere under the auroral electrojet is capable of generating extremely low frequency (ELF) radio waves in the few kilohertz range by affecting the conductivity of the D-region. The HF heating is nonlinear and results in the generation of harmonics at integer multiples of the ELF modulation frequency with ∼1% of the total power outside the fundamental when sinusoidal amplitude modulation is applied to the HF carrier. For the purpose of harmonic minimization, we present a modulation scheme designed to create a sinusoidal change in the Hall conductivity at a particular altitude in the ionosphere. The modulation waveform is generated by inverting a numerical HF heating model, starting from the desired conductivity time series, and obtaining the HF power envelope at the bottom of the ionosphere. The inverted envelopes (referred to as inv-sin waveforms) are highly sensitive to the assumed ionospheric density profile and simulations indicate that these waveforms have less harmonic distortion compared to sinusoidal modulation when the actual ionospheric density is similar to or less dense than the one assumed. Experimental results indicate that sinusoidal amplitude modulation may still be preferred since it is more robust to the highly variable ionospheric profile while square wave modulation is more efficient in generation of ELF waves when harmonic distortion is not important. The inv-sin waveforms are more efficient than sinusoidal modulation while still suffering from less harmonic distortion than square wave modulation suggesting a tradeoff between harmonic distortion and ELF generation efficiency.
Walter, W.R.
1995-06-01
The Treaty Verification Program at Lawrence Livermore National Laboratory has made good progress during fiscal year 1995 on devising and testing whole seismic waveform modeling methods to identify seismic events using only a few stations. This research is carried out under the Comprehensive Test Ban Treaty Research and Development Program (CTBTR and D) under task S4.3.4. For regions where the path is calibrated, this modeling can potentially identify and discriminate between clandestine underground nuclear events and other sources of seismic waves such as earthquakes and mine collapses. In regions where the path is not calibrated but is seismically active, the author is investigating the use of moderate to large earthquakes to obtain the necessary path calibration. Research has focused on improving whole waveform techniques for determining the source mechanism of moderate (magnitude greater than about 3.5) seismic events from a few three-component broadband sensors in regions where the paths are calibrated. Presently the author is also using these waveform techniques in new regions to test and improve path calibrations as well as to identify events. As part of this work, he has applied these waveform techniques to events of high monitoring interest with excellent results. In this report he discusses fitting three main types of events, explosions, earthquakes and mine collapses.
NASA Astrophysics Data System (ADS)
Pulliam, J.; Sen, M.
2001-12-01
Teleseismic P waves are often used to produce "receiver functions", models of the crust and upper mantle beneath stations. However, these waves arrive at a station via steep propagation angles and therefore sample only a narrow cone beneath the station, resulting in poor depth resolution. A suite of phases that arrives around the direct S phase, including Sp (converted at the base of the Moho), SsPmP, and shear-coupled PL (SPL) waves, collectively sample the medium at more oblique angles and therefore have the potential to produce a better lateral average of structural properties than teleseismic P waves. SPL waves are sensitive to velocity structure, including gradients, Vp/Vs, and layer thicknesses in the crust and uppermost mantle. The relatively large-amplitude Sp and SsPmP phases can often be modeled simultaneously with SPL, which offers the potential to constrain the model more accurately. A combination of the high frequencies required over teleseismic distances, which make the computation of synthetic seismograms time-consuming, and the complex sampling of the Earth by SPL renders trial-and-error modeling infeasible. We have parallelized and optimized a synthetic seismogram code based on the reflectivity method for use with a variant of the simulated annealing global optimization method. We are thus able to compute complete seismograms up to 0.5 Hz in just over two minutes using eight 666 MHz Alpha processors, and the speed-up in computation time is nearly linear with the number of processors used. This approach also allows us to find not only the single best-fitting solution but also its uncertainty and uniqueness. Importance sampling can be used to estimate the posterior probability function (PPD), posterior mean, covariance and correlation matrices. We model observations of S, Sp, SsPmP, and SPL recorded at stations of the China Digital Seismographic Network (CDSN) and compare our results to receiver function models produced by others. Broadband waveforms
NASA Astrophysics Data System (ADS)
Kubota, Tatsuya; Hino, Ryota; Inazu, Daisuke; Ito, Yoshihiro; Iinuma, Takeshi; Ohta, Yusaku; Suzuki, Syuichi; Suzuki, Kensuke
2017-01-01
We estimated the coseismic slip distribution associated with the Mw 7.2 and 6.5 foreshocks of the 2011 Tohoku-Oki earthquake based on analysis of the tsunami waveform records obtained just above their focal areas. The results show that the main rupture areas of each of the foreshocks do not overlap with each other, and show a distribution that is complementary to the postseismic slip area of the first Mw 7.2 foreshock as well as to the epicenters of smaller earthquakes during foreshock activity. After the second largest foreshock, seismicity increased in the area between the rupture area of the second largest foreshock and the mainshock epicenter, suggesting propagation of aseismic slip towards the mainshock epicenter. The calculated stress drop of the second largest foreshock was smaller than the largest one, implying strength reduction during the postseismic period of the largest foreshock. Based on a comparison of coastal tsunami records, it is suggested that the asperity ruptured in the M 7.0 earthquake in 1981 ruptured again during the largest foreshock in 2011, but it expanded to the updip side of the 1981 rupture area and became larger in magnitude, exemplifying the irregularity of earthquake recurrence in the area.
NASA Astrophysics Data System (ADS)
Kubo, Hisahiko; Suzuki, Wataru; Aoi, Shin; Sekiguchi, Haruko
2017-09-01
The source rupture process of the 2016 central Tottori, Japan, earthquake ( M JMA 6.6) was estimated from strong motion waveforms using a multiple-time-window kinematic waveform inversion. A large slip region with a maximum slip of 0.6 m extends from the hypocenter to the shallower part, caused by the first rupture propagating upward 0-3 s after rupture initiation. The contribution of this large slip region to the seismic waves in the frequency band of the waveform inversion is significant at all stations. Another large slip region with smaller slips was found in north-northwest of the hypocenter, caused by the second rupture propagating in the north-northwest direction at 3-5 s. Although the contribution of this slip region is not large, seismic waveforms radiating from it are necessary to explain the later part of the observed waveforms at several stations with different azimuths. The estimated seismic moment of the derived source model is 2.1 × 1018 Nm ( M w 6.1). The high-seismicity area of aftershocks did not overlap with large-slip areas of the mainshock. Two wave packets in the high frequency band observed at near-fault stations are likely to correspond to the two significant ruptures in the estimated source model.[Figure not available: see fulltext.
Multiplexed chirp waveform synthesizer
Dudley, Peter A.; Tise, Bert L.
2003-09-02
A synthesizer for generating a desired chirp signal has M parallel channels, where M is an integer greater than 1, each channel including a chirp waveform synthesizer generating at an output a portion of a digital representation of the desired chirp signal; and a multiplexer for multiplexing the M outputs to create a digital representation of the desired chirp signal. Preferably, each channel receives input information that is a function of information representing the desired chirp signal.
Parameter Estimation using Numerical Merger Waveforms
NASA Technical Reports Server (NTRS)
Thorpe, J. I.; McWilliams, S.; Kelly, B.; Fahey, R.; Arnaud, K.; Baker, J.
2008-01-01
Results: Developed parameter estimation model integrating complete waveforms and improved instrumental models. Initial results for equal-mass non-spinning systems indicate moderate improvement in most parameters, significant improvement in some Near-term improvement: a) Improved statistics; b) T-channel; c) Larger parameter space coverage. Combination with other results: a) Higher harmonics; b) Spin precession; c) Instrumental effects.
NASA Astrophysics Data System (ADS)
Saikia, C. K.; Ichinose, G. A.; Kayal, J. R.; Bhattacharya, S. N.; Shukla, A. K.
2001-12-01
The March 28, 1999 Chamoli earthquake (Mw 6.8) in northwest India generated a large sequence of aftershocks (M_ w> 4.0) which were recorded by a temporary network ofshort-period stations deployed by various organizations, namely India Meteorological Department (IMD), Geological Survey of India (GSI), National Geophysical Research Institute (NGRI) and Wadia Institute of Himalayan Geology (WIHG) in India. We inverted the local P- and S-wave arrival times from about 20 local stations jointly for all available aftershocks implementing a technique which optimizes both earthquake locations and crustal velocity model. Of these, seven events were recorded by more than 5 stations locating within 5o of the epicenters withazimuthal gap not greater than 90o. We used these events to compute the station correctionsfor local stations and applied these station corrections to relocate the entire sequence of the Chamoli aftershocks. The relocation vectors which indicate the direction toward which the events would move from the reference locations (in this case the GSI locations) suggest that for the majority of the seismic events they show movement towards the epicentral locations of the mainshock. The new locations of these events also show improvements in the error ellipse measurements. We have also investigated variations in crustal models using regional broadband seismograms from the mainshock recorded by the IMD stations in India (IMD, 2000). Using a crustal model developed earlier by Bhattacharya using surface-wave dispersion for northern India as a starting model, we conducted a systematic analysis of surface-wave dispersion characteristics recorded at these broadband stations. We synthesized f-k seismograms andexamined the relative amplitude of the Pnl waves to the surface waves and their absolutetravel-time differences. We used focal mechanism and depth that were independently determined by modeling teleseismic depth phases, pP and sP, and by modeling regional seismograms
SCA Waveform Development for Space Telemetry
NASA Technical Reports Server (NTRS)
Mortensen, Dale J.; Kifle, Multi; Hall, C. Steve; Quinn, Todd M.
2004-01-01
The NASA Glenn Research Center is investigating and developing suitable reconfigurable radio architectures for future NASA missions. This effort is examining software-based open-architectures for space based transceivers, as well as common hardware platform architectures. The Joint Tactical Radio System's (JTRS) Software Communications Architecture (SCA) is a candidate for the software approach, but may need modifications or adaptations for use in space. An in-house SCA compliant waveform development focuses on increasing understanding of software defined radio architectures and more specifically the JTRS SCA. Space requirements put a premium on size, mass, and power. This waveform development effort is key to evaluating tradeoffs with the SCA for space applications. Existing NASA telemetry links, as well as Space Exploration Initiative scenarios, are the basis for defining the waveform requirements. Modeling and simulations are being developed to determine signal processing requirements associated with a waveform and a mission-specific computational burden. Implementation of the waveform on a laboratory software defined radio platform is proceeding in an iterative fashion. Parallel top-down and bottom-up design approaches are employed.
NASA Astrophysics Data System (ADS)
Tao, Kai; Grand, Stephen P.; Niu, Fenglin
2017-09-01
In seismic full-waveform inversion (FWI), the choice of misfit function determines what information in data is used and ultimately affects the resolution of the inverted images of the Earth's structure. Misfit functions based on traveltime have been successfully applied in global and regional tomographic studies. However, wave propagation through the upper mantle results in multiple phases arriving at a given receiver in a narrow time interval resulting in complicated waveforms that evolve with distance. To extract waveform information as well as traveltime, we use a misfit function based on the normalized correlation coefficient (CC). This misfit function is able to capture the waveform complexities in both phase and relative amplitude within the measurement window. It is also insensitive to absolute amplitude differences between modeled and recorded data, which avoids problems due to uncertainties in source magnitude, radiation pattern, receiver site effects or even miscalibrated instruments. These features make the misfit function based on normalized CC a good candidate to achieve high-resolution images of complex geological structures when interfering phases coexist in the measurement window, such as triplication waveforms. From synthetic tests, we show the advantages of this misfit function over the cross-correlation traveltime misfit function. Preliminary inversion of data from an earthquake in Northeast China images a sharper and stronger amplitude slab stagnant in the middle of the transition zone than FWI of cross-correlation traveltime.
Synthetic tsunami waveform catalogs with kinematic constraints
NASA Astrophysics Data System (ADS)
Baptista, Maria Ana; Miranda, Jorge Miguel; Matias, Luis; Omira, Rachid
2017-07-01
In this study we present a comprehensive methodology to produce a synthetic tsunami waveform catalogue in the northeast Atlantic, east of the Azores islands. The method uses a synthetic earthquake catalogue compatible with plate kinematic constraints of the area. We use it to assess the tsunami hazard from the transcurrent boundary located between Iberia and the Azores, whose western part is known as the Gloria Fault. This study focuses only on earthquake-generated tsunamis. Moreover, we assume that the time and space distribution of the seismic events is known. To do this, we compute a synthetic earthquake catalogue including all fault parameters needed to characterize the seafloor deformation covering the time span of 20 000 years, which we consider long enough to ensure the representability of earthquake generation on this segment of the plate boundary. The computed time and space rupture distributions are made compatible with global kinematic plate models. We use the tsunami empirical Green's functions to efficiently compute the synthetic tsunami waveforms for the dataset of coastal locations, thus providing the basis for tsunami impact characterization. We present the results in the form of offshore wave heights for all coastal points in the dataset. Our results focus on the northeast Atlantic basin, showing that earthquake-induced tsunamis in the transcurrent segment of the Azores-Gibraltar plate boundary pose a minor threat to coastal areas north of Portugal and beyond the Strait of Gibraltar. However, in Morocco, the Azores, and the Madeira islands, we can expect wave heights between 0.6 and 0.8 m, leading to precautionary evacuation of coastal areas. The advantages of the method are its easy application to other regions and the low computation effort needed.
Anisotropic Shear-wave Velocity Structure of East Asian Upper Mantle from Waveform Tomography
NASA Astrophysics Data System (ADS)
Chong, J.; Yuan, H.; French, S. W.; Romanowicz, B. A.; Ni, S.
2012-12-01
East Asia is a seismically active region featuring active tectonic belts, such as the Himalaya collision zone, western Pacific subduction zones and the Tianshan- Baikal tectonic belt. In this study, we applied full waveform time domain tomography to image 3D isotropic, radially and azimuthally anisotropic upper mantle shear velocity structure of East Asia. High quality teleseismic waveforms were collected for both permanent and temporary stations in the target and its adjacent regions, providing good ray path coverage of the study region. Fundamental and overtone wave packets, filtered down to 60 sec, were inverted for isotropic and radially anisotropic shear wave structure using normal mode asymptotic coupling theory (NACT: Li and Romanowicz, 1995). Joint inversion of SKS measurements and seismic waveforms was then carried out following the methodology described in (Marone and Romanowicz, 2007). The 3D velocity model shows strong lateral heterogeneities in the target region, which correlate well with the surface geology in East Asia. Our model shows that Indian lithosphere has subducted beneath Tibet with a different northern reach from western to eastern Tibet,. We also find variations of the slab geometry in Western Pacific subduction zones. Old and stable regions, such as, Indian shield, Siberia platform, Tarim and Yangtze blocks are found to have higher shear wave velocity in the upper mantle. Lower velocity anomalies are found in regions like Baikal rift, Tienshan, Indochina block, and the regions along Japan island-Ryukyu Trench and Izu-bonin Trench. The dominant fast and slow velocity boundaries in the study region are well correlated with tectonic belts, such as the central Asian orogenic belt and Alty/Qilian-Qinling/Dabie orogenic belt. Our radially anisotropic model shows Vsh> Vsv in oceanic regions and at larger depths(>300km), and Vsv > Vsh in some orogenic zones.. We'll show preliminary results of azimuthally anisotropic joint inversion of SKS
Adaptive waveform optimization design for target detection in cognitive radar
NASA Astrophysics Data System (ADS)
Zhang, Xiaowen; Wang, Kaizhi; Liu, Xingzhao
2017-01-01
The problem of adaptive waveform design for target detection in cognitive radar (CR) is investigated. This problem is analyzed in signal-dependent interference, as well as additive channel noise for extended target with unknown target impulse response (TIR). In order to estimate the TIR accurately, the Kalman filter is used in target tracking. In each Kalman filtering iteration, a flexible online waveform spectrum optimization design taking both detection and range resolution into account is modeled in Fourier domain. Unlike existing CR waveform, the proposed waveform can be simultaneously updated according to the environment information fed back by receiver and radar performance demands. Moreover, the influence of waveform spectral phase to radar performance is analyzed. Simulation results demonstrate that CR with the proposed waveform performs better than a traditional radar system with a fixed waveform and offers more flexibility and suitability. In addition, waveform spectral phase will not influence tracking, detection, and range resolution performance but will greatly influence waveform forming speed and peak-to-average power ratio.
STEREO database of interplanetary Langmuir electric waveforms
NASA Astrophysics Data System (ADS)
Briand, C.; Henri, P.; Génot, V.; Lormant, N.; Dufourg, N.; Cecconi, B.; Nguyen, Q. N.; Goetz, K.
2016-02-01
This paper describes a database of electric waveforms that is available at the Centre de Données de la Physique des Plasmas (CDPP, http://cdpp.eu/). This database is specifically dedicated to waveforms of Langmuir/Z-mode waves. These waves occur in numerous kinetic processes involving electrons in space plasmas. Statistical analysis from a large data set of such waves is then of interest, e.g., to study the relaxation of high-velocity electron beams generated at interplanetary shock fronts, in current sheets and magnetic reconnection region, the transfer of energy between high and low frequencies, the generation of electromagnetic waves. The Langmuir waveforms were recorded by the Time Domain Sampler (TDS) of the WAVES radio instrument on board the STEREO mission. In this paper, we detail the criteria used to identify the Langmuir/Z-mode waves among the whole set of waveforms of the STEREO spacecraft. A database covering the November 2006 to August 2014 period is provided. It includes electric waveforms expressed in the normalized frame (B,B × Vsw,B × (B × Vsw)) with B and Vsw the local magnetic field and solar wind velocity vectors, and the local magnetic field in the variance frame, in an interval of ±1.5 min around the time of the Langmuir event. Quicklooks are also provided that display the three components of the electric waveforms together with the spectrum of E∥, together with the magnitude and components of the magnetic field in the 3 min interval, in the variance frame. Finally, the distribution of the Langmuir/Z-mode waves peak amplitude is also analyzed.
Optimal radar waveform design for moving target
NASA Astrophysics Data System (ADS)
Zhu, Binqi; Gao, Yesheng; Wang, Kaizhi; Liu, Xingzhao
2016-07-01
An optimal radar waveform-design method is proposed to detect moving targets in the presence of clutter and noise. The clutter is split into moving and static parts. Radar-moving target/clutter models are introduced and combined with Neyman-Pearson criteria to design optimal waveforms. Results show that optimal waveform for a moving target is different with that for a static target. The combination of simple-frequency signals could produce maximum detectability based on different noise-power spectrum density situations. Simulations show that our algorithm greatly improves signal-to-clutter plus noise ratio of radar system. Therefore, this algorithm may be preferable for moving target detection when prior information on clutter and noise is available.
An Improved Cryosat-2 Sea Ice Freeboard Retrieval Algorithm Through the Use of Waveform Fitting
NASA Technical Reports Server (NTRS)
Kurtz, Nathan T.; Galin, N.; Studinger, M.
2014-01-01
We develop an empirical model capable of simulating the mean echo power cross product of CryoSat-2 SAR and SAR In mode waveforms over sea ice covered regions. The model simulations are used to show the importance of variations in the radar backscatter coefficient with incidence angle and surface roughness for the retrieval of surfaceelevation of both sea ice floes and leads. The numerical model is used to fit CryoSat-2 waveforms to enable retrieval of surface elevation through the use of look-up tables and a bounded trust region Newton least squares fitting approach. The use of a model to fit returns from sea ice regions offers advantages over currently used threshold retrackingmethods which are here shown to be sensitive to the combined effect of bandwidth limited range resolution and surface roughness variations. Laxon et al. (2013) have compared ice thickness results from CryoSat-2 and IceBridge, and found good agreement, however consistent assumptions about the snow depth and density of sea ice werenot used in the comparisons. To address this issue, we directly compare ice freeboard and thickness retrievals from the waveform fitting and threshold tracker methods of CryoSat-2 to Operation IceBridge data using a consistent set of parameterizations. For three IceBridge campaign periods from March 20112013, mean differences (CryoSat-2 IceBridge) of 0.144m and 1.351m are respectively found between the freeboard and thickness retrievals using a 50 sea ice floe threshold retracker, while mean differences of 0.019m and 0.182m are found when using the waveform fitting method. This suggests the waveform fitting technique is capable of better reconciling the seaice thickness data record from laser and radar altimetry data sets through the usage of consistent physical assumptions.
An improved algorithm for inferring neutron star masses and radii using NICER waveform data
NASA Astrophysics Data System (ADS)
Lamb, Frederick K.; Miller, M. Coleman
2015-01-01
We have developed a new, faster Bayesian analysis algorithm that enables us to use energy-resolved waveforms of X-ray burst oscillations, like those that will be obtained using NICER, to estimate quickly the masses and radii of rapidly rotating, oblate neutron stars and determine the uncertainties in these estimates. We use the oblate-Schwarzschild (OS) approximation, which Cadeau et al. (2007) showed provides a very accurate description of the waveforms produced by hot spots on rapidly rotating, oblate neutron stars. We show that the angular radius of the hot spot and a phase-independent but otherwise arbitrary background must be included as part of the fit; to do otherwise is observationally incorrect and leads to misleadingly tight constraints on the mass and radius. A simple, single-hot-spot waveform model with 30 energy channels has 38 parameters. If the waveform data is informative, i.e., if they tightly constrain the mass M and the equatorial radius R of the star, the high-probability regions of the full parameter space are small. A grid search of this space would therefore require a prohibitive number of waveform computations. Here we describe a different procedure that is much more efficient. This new procedure (1) generates waveforms by interpolating in a table of pre-computed waveforms and (2) computes bounding ellipsoids that encompass points in the waveform parameter space that have interestingly high likelihoods. Using these bounding ellipsoids typically reduces the volume of the Monte Carlo integration by a factor ~ 30. The net result of these improvements is that whereas the analysis procedure used in Lo et al. (2013) took 50-150 clock hours on a 150-core cluster and did not search the (M,R) volume of interest, the new analysis procedure takes 50-150 clock hours on a 5-core desktop computer to perform a completely blind search of the full volume, despite the additional complexity of the OS waveform model used in the new algorithm.
Seismic moment tensor inversion using a 3-D structural model: applications for the Australian region
NASA Astrophysics Data System (ADS)
Hingee, Myall; Tkalčić, Hrvoje; Fichtner, Andreas; Sambridge, Malcolm
2011-02-01
There is significant seismic activity in the region around Australia, largely due to the plate boundaries to the north and to the east of the mainland. This activity results in serious seismic and tsunami hazard in the coastal areas of Australia. Hence seismicity is and will be monitored in real time by Geoscience Australia (GA), which uses a network of permanent broadband seismometers. Seismic moment tensor (MT) solutions are currently determined using 1-D, radially symmetric models of Earth and this requires augmentation by recording stations located outside of Australia. A 3-D model of the Australian continent developed recently using full waveform tomography now offers the opportunity to significantly improve the determination of MT solutions of earthquakes from tectonically active regions. A complete-waveform, time-domain MT inversion method has been developed using a point-source approximation. A series of synthetic tests using first a 1-D and then a 3-D structural model has been performed. The feasibility of deploying 3-D versus 1-D Earth structure for the inversion of seismic data has been studied and the advantages of using the 3-D structural model were illustrated with examples. The 3-D model is superior to the 1-D model, as a number of sensitivity tests show. The ultimate goal of this work is an automated MT inversion system in Australia relying on GA and other international stations, although more work remains to be done before the full implementation of such a scheme in real time.
High precision triangular waveform generator
Mueller, Theodore R.
1983-01-01
An ultra-linear ramp generator having separately programmable ascending and descending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.
Direct distribution model for regional aquatic acidification
Small, M.J.; Sutton, M.C.
1986-12-01
A model is developed to predict the regional distribution of lake acidification and its effect on fish survival. The model predicts the effect of changes in acid deposition rates on the mean and variance of the regional distribution of lake alkalinity using empirical weathering models with variable weathering factors. The regional distribution of lake alkalinity is represented by a three-parameters lognormal distribution. The regional pH distribution is derived using an explicit pH-alkalinity relationship. The predicted pH distribution is combined with a fish presence-absence relationship to predict the fraction of lakes in a region able to support fish. The model is illustrated with a set of 1014 lakes in the Adirondack Park region of New York State. Significant needs for future research for regional aggregation of aquatic acidification models are identified.
Regions in Energy Market Models
2009-01-18
This report explores the different options for spatial resolution of an energy market model and the advantages and disadvantages of models with fine spatial resolution. It examines different options for capturing spatial variations, considers the tradeoffs between them, and presents a few examples from one particular model that has been run at different levels of spatial resolution.
Regions in Energy Market Models
Short, W.
2007-02-01
This report explores the different options for spatial resolution of an energy market model--and the advantages and disadvantages of models with fine spatial resolution. It examines different options for capturing spatial variations, considers the tradeoffs between them, and presents a few examples from one particular model that has been run at different levels of spatial resolution.
Finley, Andrew O.; Banerjee, Sudipto; Cook, Bruce D.; Bradford, John B.
2013-01-01
In this paper we detail a multivariate spatial regression model that couples LiDAR, hyperspectral and forest inventory data to predict forest outcome variables at a high spatial resolution. The proposed model is used to analyze forest inventory data collected on the US Forest Service Penobscot Experimental Forest (PEF), ME, USA. In addition to helping meet the regression model's assumptions, results from the PEF analysis suggest that the addition of multivariate spatial random effects improves model fit and predictive ability, compared with two commonly applied modeling approaches. This improvement results from explicitly modeling the covariation among forest outcome variables and spatial dependence among observations through the random effects. Direct application of such multivariate models to even moderately large datasets is often computationally infeasible because of cubic order matrix algorithms involved in estimation. We apply a spatial dimension reduction technique to help overcome this computational hurdle without sacrificing richness in modeling.
NASA Astrophysics Data System (ADS)
Altunc, Serhat; Baum, Carl E.; Christodoulou, Christos G.; Schamiloglu, Edl; Buchenauer, C. Jerald
2008-08-01
Impulse radiating antennas (IRAs) are designed to radiate very fast pulses in a narrow beam with low dispersion and high field amplitude. For this reason they have been used in a variety of applications. IRAs have been developed for use in the transient far-field region using parabolic reflectors. However, in this paper we focus in the near field region and develop the field waveform at the second focus of a prolate-spheroidal IRA. Certain skin cancers can be killed by the application of a high-amplitude electric field pulse. This can be accomplished by either inserting electrodes near the skin cancer or by applying fast, high-electric field pulses without direct contact. We investigate a new manifestation of an IRA, in which we use a prolate spheroid as a reflector instead of a parabolic reflector and focus in the near-field region instead of the far-field region. This technique minimizes skin damage associated with inserting electrodes near the tumor. Analytical and experimental behaviors for the focal waveforms of two and four-feed arm prolate-spheroidal IRAs are explored. With appropriate choice of the driving waveform we maximize the impulse field at the second focus. The focal waveform of a prolate-spheroidal IRA has been explained theoretically and verified experimentally.
The Waveform Server: A Web-based Interactive Seismic Waveform Interface
NASA Astrophysics Data System (ADS)
Newman, R. L.; Clemesha, A.; Lindquist, K. G.; Reyes, J.; Steidl, J. H.; Vernon, F. L.
2009-12-01
Seismic waveform data has traditionally been displayed on machines that are either local area networked to, or directly host, a seismic networks waveform database(s). Typical seismic data warehouses allow online users to query and download data collected from regional networks passively, without the scientist directly visually assessing data coverage and/or quality. Using a suite of web-based protocols, we have developed an online seismic waveform interface that directly queries and displays data from a relational database through a web-browser. Using the Python interface to Datascope and the Python-based Twisted network package on the server side, and the jQuery Javascript framework on the client side to send and receive asynchronous waveform queries, we display broadband seismic data using the HTML Canvas element that is globally accessible by anyone using a modern web-browser. The system is used to display data from the USArray experiment, a US continent-wide migratory transportable seismic array. We are currently creating additional interface tools to create a rich-client interface for accessing and displaying seismic data that can be deployed to any system running Boulder Real Time Technology's (BRTT) Antelope Real Time System (ARTS). The software is freely available from the Antelope contributed code Git repository. Screenshot of the web-based waveform server interface
STRS Compliant FPGA Waveform Development
NASA Technical Reports Server (NTRS)
Nappier, Jennifer; Downey, Joseph; Mortensen, Dale
2008-01-01
The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. The extension of STRS to the SSP hardware will promote easier waveform reconfiguration and reuse. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. A FPGA-based transmit waveform implementation of the proposed standard interfaces on a laboratory breadboard SDR will be discussed.
Freytag, D.R.; Haller, G.M.; Kang, H.; Wang, J.
1985-09-01
A Waveform Sampler Module (WSM) for the measurement of signal shapes coming from the multi-hit drift chambers of the SLAC SLC detector is described. The module uses a high speed, high resolution analog storage device (AMU) developed in collaboration between SLAC and Stanford University. The AMU devices together with high speed TTL clocking circuitry are packaged in a hybrid which is also suitable for mounting on the detector. The module is in CAMAC format and provides eight signal channels, each recording signal amplitude versus time in 512 cells at a sampling rate of up to 360 MHz. Data are digitized by a 12-bit ADC with a 1 ..mu..s conversion time and stored in an on-board memory accessible through CAMAC.
Ingnet On-line: The 1988-2002 Ingv Seismic Waveforms Database
NASA Astrophysics Data System (ADS)
di Stefano, R.; Amato, A.; Mele, F.; Kissling, E.
The increasing need for global information exchange is strongly influencing data us- age and sharing in public research. Seismological sciences also greatly benefit from this change in data exchange policy. In Eurasia several national seismic networks have been continuously active since the first part of the last century and numerous seismo- logical services exist for the past few decades. Hence, a large number of analog and digital waveforms have been recorded, though the data from different services, with a few exceptions, remain unmerged. In the Italian peninsula (western Mediterranean region) the INGV National Seismic Network recorded more than 80.000 earthquakes during the last 20 years, 68.000 of which have waveforms in digital format (with more than 250.000 recordings). We present first results of a joint project between INGV and ETH, to obtain a high-resolution seismic velocity model for the Italian peninsula and surrounding regions. In a first step all available waveforms have been extracted and re-organized in a new database that will be soon open to the international scien- tific community through an easy-to-access internet front-end. Waveforms have been converted from an internal INGV format to the widely known and used SAC format completing the headers with all information necessary for a wide range of seismologi- cal investigations. We present here the structure of this database and its characteristics, and the conditions for accessibility through the INGV web site.
Vannier, E; Avan, P
2005-10-01
Transient-evoked otoacoustic emissions (TEOAE) are widely used for objective hearing screening in neonates. Their main shortcoming is their sensitivity to adverse conditions for sound transmission through the middle-ear, to and from the cochlea. We study here whether a close examination of the stimulus waveform (SW) recorded in the ear canal in the course of a screening test can pinpoint the most frequent middle-ear dysfunctions, thus allowing screeners to avoid misclassifying the corresponding babies as deaf for lack of TEOAE. Three groups of SWs were defined in infants (6-36 months of age) according to middle-ear impairment as assessed by independent testing procedures, and analyzed in the frequency domain where their properties are more readily interpreted than in the time domain. Synthetic SW parameters were extracted with the help of an autoregressive and moving average (ARMA) model, then classified using a maximum likelihood criterion and a bootstrap cross-validation. The best classification performance was 79% with a lower limit (with 90% confidence) of 60%, showing the results' consistency. We therefore suggest that new parameters and methodology based upon a more thorough analysis of SWs can improve the efficiency of TEOAE-based tests by helping the most frequent technical pitfalls to be identified.
Regional fuzzy chain model for evapotranspiration estimation
NASA Astrophysics Data System (ADS)
Güçlü, Yavuz Selim; Subyani, Ali M.; Şen, Zekai
2017-01-01
Evapotranspiration (ET) is one of the main hydrological cycle components that has extreme importance for water resources management and agriculture especially in arid and semi-arid regions. In this study, regional ET estimation models based on the fuzzy logic (FL) principles are suggested, where the first stage includes the ET calculation via Penman-Monteith equation, which produces reliable results. In the second phase, ET estimations are produced according to the conventional FL inference system model. In this paper, regional fuzzy model (RFM) and regional fuzzy chain model (RFCM) are proposed through the use of adjacent stations' data in order to fill the missing ones. The application of the two models produces reliable and satisfactory results for mountainous and sea region locations in the Kingdom of Saudi Arabia, but comparatively RFCM estimations have more accuracy. In general, the mean absolute percentage error is less than 10%, which is acceptable in practical applications.
NASA Astrophysics Data System (ADS)
Ma, L.; Zhou, M.; Li, C.
2017-09-01
In this study, a Random Forest (RF) based land covers classification method is presented to predict the types of land covers in Miyun area. The returned full-waveforms which were acquired by a LiteMapper 5600 airborne LiDAR system were processed, including waveform filtering, waveform decomposition and features extraction. The commonly used features that were distance, intensity, Full Width at Half Maximum (FWHM), skewness and kurtosis were extracted. These waveform features were used as attributes of training data for generating the RF prediction model. The RF prediction model was applied to predict the types of land covers in Miyun area as trees, buildings, farmland and ground. The classification results of these four types of land covers were obtained according to the ground truth information acquired from CCD image data of the same region. The RF classification results were compared with that of SVM method and show better results. The RF classification accuracy reached 89.73% and the classification Kappa was 0.8631.
Seismic Waveform Characterization at LLNL: Analyst Guidelines and Issues
Ryall, F; Schultz, C A
2001-11-01
In the first section of this paper we present an overview of general set of procedures that we have followed in seismic waveform analysis. In the second section we discuss a number of issues and complexities that we have encountered in analysis of events in the Middle East, North Africa, Europe, and parts of the European Arctic. To illustrate these complexities we can include examples of waveforms recorded over a variety of paths in these regions.
Regional Climate Modeling: Progress, Challenges, and Prospects
Wang, Yuqing; Leung, Lai R.; McGregor, John L.; Lee, Dong-Kyou; Wang, Wei-Chyung; Ding, Yihui; Kimura, Fujio
2004-12-01
Regional climate modeling with regional climate models (RCMs) has matured over the past decade and allows for meaningful utilization in a broad spectrum of applications. In this paper, latest progresses in regional climate modeling studies are reviewed, including RCM development, applications of RCMs to dynamical downscaling for climate change assessment, seasonal climate predictions and climate process studies, and the study of regional climate predictability. Challenges and potential directions of future research in this important area are discussed, with the focus on those to which less attention has been given previously, such as the importance of ensemble simulations, further development and improvement of regional climate modeling approach, modeling extreme climate events and sub-daily variation of clouds and precipitation, model evaluation and diagnostics, applications of RCMs to climate process studies and seasonal predictions, and development of regional earth system models. It is believed that with both the demonstrated credibility of RCMs’ capability in reproducing not only monthly to seasonal mean climate and interannual variability but also the extreme climate events when driven by good quality reanalysis and the continuous improvements in the skill of global general circulation models (GCMs) in simulating large-scale atmospheric circulation, regional climate modeling will remain an important dynamical downscaling tool for providing the needed information for assessing climate change impacts and seasonal climate predictions, and a powerful tool for improving our understanding of regional climate processes. An internationally coordinated effort can be developed with different focuses by different groups to advance regional climate modeling studies. It is also recognized that since the final quality of the results from nested RCMs depends in part on the realism of the large-scale forcing provided by GCMs, the reduction of errors and improvement in
Adaptive multi-step Full Waveform Inversion based on Waveform Mode Decomposition
NASA Astrophysics Data System (ADS)
Hu, Yong; Han, Liguo; Xu, Zhuo; Zhang, Fengjiao; Zeng, Jingwen
2017-04-01
Full Waveform Inversion (FWI) can be used to build high resolution velocity models, but there are still many challenges in seismic field data processing. The most difficult problem is about how to recover long-wavelength components of subsurface velocity models when seismic data is lacking of low frequency information and without long-offsets. To solve this problem, we propose to use Waveform Mode Decomposition (WMD) method to reconstruct low frequency information for FWI to obtain a smooth model, so that the initial model dependence of FWI can be reduced. In this paper, we use adjoint-state method to calculate the gradient for Waveform Mode Decomposition Full Waveform Inversion (WMDFWI). Through the illustrative numerical examples, we proved that the low frequency which is reconstructed by WMD method is very reliable. WMDFWI in combination with the adaptive multi-step inversion strategy can obtain more faithful and accurate final inversion results. Numerical examples show that even if the initial velocity model is far from the true model and lacking of low frequency information, we still can obtain good inversion results with WMD method. From numerical examples of anti-noise test, we see that the adaptive multi-step inversion strategy for WMDFWI has strong ability to resist Gaussian noise. WMD method is promising to be able to implement for the land seismic FWI, because it can reconstruct the low frequency information, lower the dominant frequency in the adjoint source, and has a strong ability to resist noise.
Unveiling Hidden Unstructured Regions in Process Models
NASA Astrophysics Data System (ADS)
Polyvyanyy, Artem; García-Bañuelos, Luciano; Weske, Mathias
Process models define allowed process execution scenarios. The models are usually depicted as directed graphs, with gateway nodes regulating the control flow routing logic and with edges specifying the execution order constraints between tasks. While arbitrarily structured control flow patterns in process models complicate model analysis, they also permit creativity and full expressiveness when capturing non-trivial process scenarios. This paper gives a classification of arbitrarily structured process models based on the hierarchical process model decomposition technique. We identify a structural class of models consisting of block structured patterns which, when combined, define complex execution scenarios spanning across the individual patterns. We show that complex behavior can be localized by examining structural relations of loops in hidden unstructured regions of control flow. The correctness of the behavior of process models within these regions can be validated in linear time. These observations allow us to suggest techniques for transforming hidden unstructured regions into block-structured ones.
NASA Astrophysics Data System (ADS)
Moghadas, D.; André, F.; Vereecken, H.; Lambot, S.
2009-04-01
Water is a vital resource for human needs, agriculture, sanitation and industrial supply. The knowledge of soil water dynamics and solute transport is essential in agricultural and environmental engineering as it controls plant growth, hydrological processes, and the contamination of surface and subsurface water. Increased irrigation efficiency has also an important role for water conservation, reducing drainage and mitigating some of the water pollution and soil salinity. Geophysical methods are effective techniques for monitoring the vadose zone. In particular, electromagnetic induction (EMI) can provide in a non-invasive way important information about the soil electrical properties at the field scale, which are mainly correlated to important variables such as soil water content, salinity, and texture. EMI is based on the radiation of a VLF EM wave into the soil. Depending on its electrical conductivity, Foucault currents are generated and produce a secondary EM field which is then recorded by the EMI system. Advanced techniques for EMI data interpretation resort to inverse modeling. Yet, a major gap in current knowledge is the limited accuracy of the forward model used for describing the EMI-subsurface system, usually relying on strongly simplifying assumptions. We present a new low frequency EMI method based on Vector Network Analyzer (VNA) technology and advanced forward modeling using a linear system of complex transfer functions for describing the EMI loop antenna and a three-dimensional solution of Maxwell's equations for wave propagation in multilayered media. VNA permits simple, international standard calibration of the EMI system. We derived a Green's function for the zero-offset, off-ground horizontal loop antenna and also proposed an optimal integration path for faster evaluation of the spatial-domain Green's function from its spectral counterpart. This new integration path shows fewer oscillations compared with the real path and permits to avoid the
Thermal modeling of forearc regions
Kominz, M. A.; Bond, G. C.
1989-08-01
The unconventional natural gas resource program of the Department of Energy has targeted ancient subduction zones as a possible source of organic-origin natural gas. The suggestion is that organic sediments which have been accreted in the prism and/or subducted beneath the prism will produce gas at greater depths than in more conventional, generally hotter, basins. A critical element in determining the likelihood of gas generation in ancient or modern accretionary prisms is the thermal regime of the accreting prism. We have developed a computer model to determine the overall thermal regime in the modern forearcs of Oregon/Washington and southern Alaska. This allows us to predict the likelihood that gas has been generated at depth in the forearc prism, or within sediments as they are subducted beneath the prism. In fact, the model results indicate that subduction and accretion of these sediments at low temperatures increases the probability that ancient subduction zones, once accreted to the craton and allowed to heat in response to migration of the volcanic front, could be the source of natural gas. 75 refs., 24 figs.
Thermal modeling of forearc regions
Kominz, M.A.; Bond, G.C.
1989-08-01
The unconventional natural gas resource program of the Department of Energy has targeted ancient subduction zones as a possible source of organic-origin natural gas. The suggestion is that organic sediments which have been accreted in the prism and/or subducted beneath the prism will produce gas at greater depths than in more conventional, generally hotter, basins. A critical element in determining the likelihood of gas generation in ancient or modern accretionary prisms is the thermal regime of the accreting prism. We have developed a computer model to determine the overall thermal regime in the modern forearcs of Oregon/Washington and southern Alaska. This allows us to predict the likelihood that gas has been generated at depth in the forearc prism, or within sediments as they are subducted beneath the prism. In fact, the model results indicate that subduction and accretion of these sediments at low temperatures increases the probability that ancient subduction zones, once accreted to the craton and allowed to heat in response to migration of the volcanic front, could be the source of natural gas. 75 refs., 24 figs.
NASA Astrophysics Data System (ADS)
Kang, S. G.; Hong, J. K.; Jin, Y. K.; Kim, S.; Kim, Y. G.; Dallimore, S.; Riedel, M.; Shin, C.
2015-12-01
During Expedition ARA05C (from Aug 26 to Sep 19, 2014) on the Korean icebreaker RV ARAON, the multi-channel seismic (MCS) data were acquired on the outer shelf and slope of the Canadian Beaufort Sea to investigate distribution and internal geological structures of the offshore ice-bonded permafrost and gas hydrates, totaling 998 km L-km with 19,962 shots. The MCS data were recorded using a 1500 m long solid-type streamer with 120 channels. Shot and group spacing were 50 m and 12.5 m, respectively. Most MCS survey lines were designed perpendicular and parallel to the strike of the shelf break. Ice-bonded permafrost or ice-bearing sediments are widely distributed under the Beaufort Sea shelf, which have formed during periods of lower sea level when portions of the shelf less than ~100m water depth were an emergent coastal plain exposed to very cold surface. The seismic P-wave velocity is an important geophysical parameter for identifying the distribution of ice-bonded permafrost with high velocity in this area. Recently, full waveform inversion (FWI) and reverse time migration (RTM) are commonly used to delineate detailed seismic velocity information and seismic image of geological structures. FWI is a data fitting procedure based on wave field modeling and numerical analysis to extract quantitative geophysical parameters such as P-, S-wave velocities and density from seismic data. RTM based on 2-way wave equation is a useful technique to construct accurate seismic image with amplitude preserving of field data. In this study, we suggest two-dimensional P-wave velocity model (Figure.1) using the FWI algorithm to delineate the top and bottom boundaries of ice-bonded permafrost in the Canadian shelf of Beaufort Sea. In addition, we construct amplitude preserving migrated seismic image using RTM to interpret the geological history involved with the evolution of permafrost.
NASA Astrophysics Data System (ADS)
Yuan, S.; Fuji, N.; Singh, S. C.; Borisov, D.
2016-12-01
We present a novel methodology to invert seismic data locally through the combination of wavefield injection and extrapolation method. Seismic full waveform inversion has proved its promising resolving power in seismology community for these decades. However, the computational cost for 3D practical scale elastic or viscoelastic waveform inversion remains still challenging. The computational cost is much more severe for time-lapse surveys, which requires real-time model estimation on a daily or weekly basis. Besides, changes of the structures during time-lapse surveys are likely to occur within a smaller area, such as oil and gas reservoir or CO2 injection wells. We propose methods that effectively and quantitatively image the localized structure change relatively far from source and receiver arrays. We thus have to perform both forward modeling and waveform inversions inside the region that contain neither source nor receiver. Firstly, we look for the equivalent source expression inside the region of interest by wavefield injection method. Secondly, we extrapolate wavefield from physical receivers to an array of virtual receivers by using correlation-type representation theorem. In this paper, we present elastic 2D numerical examples of our methods and quantitatively evaluate errors of obtained models, in comparison with those from full-model inversions. The results show that the proposed localized waveform inversion is more efficient, accurate and robust even under existence of errors in both initial models and data.
NASA Astrophysics Data System (ADS)
Rodríguez Cardozo, Félix; Hjörleifsdóttir, Vala; Caló, Marco
2017-04-01
Moment tensor inversions for intermediate and small earthquakes (M. < 4.5) are challenging as they principally excite relatively short period seismic waves that interact strongly with local heterogeneities. Incorporating detailed regional 3D velocity models permits obtaining realistic synthetic seismograms and recover the seismic source parameters these smaller events. Two 3D regional velocity models have recently been developed for Mexico, using surface waves and seismic noise tomography (Spica et al., 2016; Gaite et al., 2015), which could be used to model the waveforms of intermediate magnitud earthquakes in this region. Such models are parameterized as layered velocity profiles and for some of the profiles, the velocity difference between two layers are considerable. The "jump" in velocities between two layers is inconvenient for some methods and algorithms that calculate synthetic waveforms, in particular for the method that we are using, the spectral element method (SPECFEM3D GLOBE, Komatitsch y Tromp, 2000), when the mesh does not follow the layer boundaries. In order to make the velocity models more easily implementec in SPECFEM3D GLOBE it is neccesary to apply a homogenization algorithm (Capdeville et al., 2015) such that the (now anisotropic) layer velocities are smoothly varying with depth. In this work, we apply a homogenization algorithm to the regional velocity models in México for implementing them in SPECFEM3D GLOBE, calculate synthetic waveforms for intermediate-magnitude earthquakes in México and invert them for the seismic moment tensor.
NASA Astrophysics Data System (ADS)
Monteiller, Vadim; Chevrot, Sébastien; Komatitsch, Dimitri; Wang, Yi
2015-08-01
We present a method for high-resolution imaging of lithospheric structures based on full waveform inversion of teleseismic waveforms. We model the propagation of seismic waves using our recently developed direct solution method/spectral-element method hybrid technique, which allows us to simulate the propagation of short-period teleseismic waves through a regional 3-D model. We implement an iterative quasi-Newton method based upon the L-BFGS algorithm, where the gradient of the misfit function is computed using the adjoint-state method. Compared to gradient or conjugate-gradient methods, the L-BFGS algorithm has a much faster convergence rate. We illustrate the potential of this method on a synthetic test case that consists of a crustal model with a crustal discontinuity at 25 km depth and a sharp Moho jump. This model contains short- and long-wavelength heterogeneities along the lateral and vertical directions. The iterative inversion starts from a smooth 1-D model derived from the IASP91 reference Earth model. We invert both radial and vertical component waveforms, starting from long-period signals filtered at 10 s and gradually decreasing the cut-off period down to 1.25 s. This multiscale algorithm quickly converges towards a model that is very close to the true model, in contrast to inversions involving short-period waveforms only, which always get trapped into a local minimum of the cost function.
An Evaluation of Regionalized Models for Eurasia
NASA Astrophysics Data System (ADS)
Tkalcic, H.; Laske, G.
2002-12-01
This study evaluates recently developed regionalized models of the crust and upper mantle for Western Eurasia and Northern Africa. Such models are typically used in the CTBT effort to improve event location in regions of political interest, to model wave propagation of regional phases and to correct seismic data for the crustal contribution. We examine the SAIC model 1.0 (Bondar, 2000), the LLNL model MENA1.1 (Walter et al., 2000) and global crustal models CRUST5.1 (Mooney et al., 1998) and CRUST2.0 (Bassin et al., 2000). These models use a relatively limited number of crustal types to describe lateral variations in structure. We investigate the feasibility of using such simple models to represent crucial parameters of the true Earth, such as crustal and sediment thickness, without a great loss of accuracy. To test this, we use the 1x1 degree digital sediment thickness map of Laske and Masters (1997) and a newly compiled 1x1 crustal thickness map as references models. In general, we find good agreement between the crustal thickness reference map and the regionalized models MENA1.1 and SAIC1.0, but significant disagreement can occur in the sediment thickness. We also identify errors in CRUST5.1. We conclude that, in contrast to crustal thickness, sediment thickness cannot be categorized using tectonic setting or basement age as criteria. We also test how accurately the regionalized models predict seismic data. We compare model predictions with observed surface wave phase and group velocity maps. For each region categorized in the models, we examine histograms of the data and compare the average dispersion values with the model predictions. This comparison confirms that some regions require a change in the structure specified and/or an additional subdivision of this region. Some regions appear quite complex, perhaps inhibiting a simple regionalization altogether. Our results show that simple crustal models may oversimplify the structure of the real Earth which can
Hybridizing Gravitationl Waveforms of Inspiralling Binary Neutron Star Systems
NASA Astrophysics Data System (ADS)
Cullen, Torrey; LIGO Collaboration
2016-03-01
Gravitational waves are ripples in space and time and were predicted to be produced by astrophysical systems such as binary neutron stars by Albert Einstein. These are key targets for Laser Interferometer and Gravitational Wave Observatory (LIGO), which uses template waveforms to find weak signals. The simplified template models are known to break down at high frequency, so I wrote code that constructs hybrid waveforms from numerical simulations to accurately cover a large range of frequencies. These hybrid waveforms use Post Newtonian template models at low frequencies and numerical data from simulations at high frequencies. They are constructed by reading in existing Post Newtonian models with the same masses as simulated stars, reading in the numerical data from simulations, and finding the ideal frequency and alignment to ``stitch'' these waveforms together.
General Dynamic (GD) Launch Waveform On-Orbit Performance Report
NASA Technical Reports Server (NTRS)
Briones, Janette C.; Shalkhauser, Mary Jo
2014-01-01
The purpose of this report is to present the results from the GD SDR on-orbit performance testing using the launch waveform over TDRSS. The tests include the evaluation of well-tested waveform modes, the operation of RF links that are expected to have high margins, the verification of forward return link operation (including full duplex), the verification of non-coherent operational models, and the verification of radio at-launch operational frequencies. This report also outlines the launch waveform tests conducted and comparisons to the results obtained from ground testing.
Analytic gravitational waveforms for generic precessing compact binaries
NASA Astrophysics Data System (ADS)
Chatziioannou, Katerina; Klein, Antoine; Cornish, Neil; Yunes, Nicolas
2017-01-01
Gravitational waves from compact binaries are subject to amplitude and phase modulations arising from interactions between the angular momenta of the system. Failure to account for such spin-precession effects in gravitational wave data analysis could hinder detection and completely ruin parameter estimation. In this talk I will describe the construction of closed-form, frequency-domain waveforms for fully-precessing, quasi-circular binary inspirals. The resulting waveforms can model spinning binaries of arbitrary spin magnitudes, spin orientations, and masses during the inspiral phase. I will also describe ongoing efforts to extend these inspiral waveforms to the merger and ringdown phases.
Effective waveform recorder evaluation procedures
NASA Astrophysics Data System (ADS)
Green, Philip J.
The evaluation of waveform recorders is a subject attracting considerable attention as waveform recorders continue to increase in capabilities without dramatic increase in costs. However, caution is required when developing evaluation procedures because of the potential of any evaluation procedure to overestimate the performance of a device. A system is described which is controlled by a Microvax II with instrumentation control through the IEEE-488 bus. Evaluation procedures are described with attention given to the pathological cases which can lead to significant misestimates of a digitizer's performance. These evaluation procedures are aimed at being consistent with the new Trial Waveform Digitizer Standard generated by the Waveform Measurements and Analysis committee appointed by the Instrumentation and Measurement Society of IEEE. This standard was recently accepted by the IEEE as a trial use standard through July 1991 and is available from the IEEE Service Center as IEEE Std. 1057.
Simulation of Full-Waveform Laser Altimeter Echowaveform
NASA Astrophysics Data System (ADS)
Lv, Y.; Tong, X. H.; Liu, S. J.; Xie, H.; Luan, K. F.; Liu, J.
2016-06-01
Change of globe surface height is an important factor to study human living environment. The Geoscience Laser Altimeter System (GLAS) on ICESat is the first laser-ranging instrument for continuous global observations of the Earth. In order to have a comprehensive understanding of full-waveform laser altimeter, this study simulated the operating mode of ICESat and modeled different terrains' (platform terrain, slope terrain, and artificial terrain) echo waveforms based on the radar equation. By changing the characteristics of the system and the targets, numerical echo waveforms can be achieved. Hereafter, we mainly discussed the factors affecting the amplitude and size (width) of the echoes. The experimental results implied that the slope of the terrain, backscattering coefficient and reflectivity, target height, target position in the footprint and area reacted with the pulse all can affect the energy distribution of the echo waveform and the receiving time. Finally, Gaussian decomposition is utilized to decompose the echo waveform. From the experiment, it can be noted that the factors which can affect the echo waveform and by this way we can know more about large footprint full-waveform satellite laser altimeter.
STRS Compliant FPGA Waveform Development
NASA Technical Reports Server (NTRS)
Nappier, Jennifer; Downey, Joseph
2008-01-01
The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. Current standards were researched and new standard interfaces were proposed. The implementation of the proposed standard interfaces on a laboratory breadboard SDR will be presented.
Prismatic and full-waveform joint inversion
NASA Astrophysics Data System (ADS)
Qu, Ying-Ming; Li, Zhen-Chun; Huang, Jian-Ping; Li, Jin-Li
2016-09-01
Prismatic wave is that it has three reflection paths and two reflection points, one of which is located at the reflection interface and the other is located at the steep dip angle reflection layer, so that contains a lot of the high and steep reflection interface information that primary cannot reach. Prismatic wave field information can be separated by applying Born approximation to traditional reverse time migration profile, and then the prismatic wave is used to update velocity to improve the inversion efficiency for the salt dame flanks and some other high and steep structure. Under the guidance of this idea, a prismatic waveform inversion method is proposed (abbreviated as PWI). PWI has a significant drawback that an iteration time of PWI is more than twice as that of FWI, meanwhile, the full wave field information cannot all be used, for this problem, we propose a joint inversion method to combine prismatic waveform inversion with full waveform inversion. In this method, FWI and PWI are applied alternately to invert the velocity. Model tests suggest that the joint inversion method is less dependence on the high and steep structure information in the initial model and improve high inversion efficiency and accuracy for the model with steep dip angle structure.
NASA Astrophysics Data System (ADS)
Górszczyk, A.; Malinowski, M.; Operto, S.
2016-12-01
Since decades wide-angle reflection/refraction (WARR) surveys and ray-based methods, remain typical tools for the marine crustal-scale velocity model building. Still however they ability to resolve complex structures is limited by factors such like: OBS spacing, width of the Fresnel zone or interpreter's ability to distinguish and associate the crustal phases with the crustal interfaces. Alternatively we present multiscale, layer-stripping strategy for the semi-automatic, high resolution, crustal-scale imaging using Full Waveform Inversion (FWI).We develop practical workflow including: (i) preprocessing focused on the improvement of the coherency and boost of the low frequencies; (ii) thorough and early stage QC starting from the analysis of the traveltime error in the initial model; (iii) final model validation procedures using source estimation, evaluation of the datafitting with Dynamic Image Warping, correlation with PSDM image and the interpretation of crustal phases by the ray-tracing. We successfully apply this workflow to the 2D OBS dataset from the Eastern Nankai Through involving 100 OBS uniformly deployed along a 100-km long profile recording air-gun shots extended along 140-km long profile with a 100 m spacing.As a result we obtain velocity model of the complex subduction zone with clearly delineated shallow and deep structures. In particular in the Backstop we observe large-scale stacked thrust sheets of Shimanto Wedge covered by sediments of Forearc Basin. These structures spatially extend to the area of Miocene Wedge in Accretionary Prism forming Kodaiba and Tokai Thrusts. Further into seaward direction we can point sequence of smaller thrusts delineating Active Wedge covered by Slope Basins and the thick layers of sediments in the trench. We observe local thickening of the oceanic crust corresponding to the subducting oceanic ridges as well as a sharp LVZ atop the oceanic crust which represent a damage fault zone created by one of these ridges
NASA Astrophysics Data System (ADS)
Lackey, Benjamin D.; Kyutoku, Koutarou; Shibata, Masaru; Brady, Patrick R.; Friedman, John L.
2014-02-01
Information about the neutron-star equation of state is encoded in the waveform of a black hole-neutron star system through tidal interactions and the possible tidal disruption of the neutron star. During the inspiral this information depends on the tidal deformability Λ of the neutron star, and we find that the best-measured parameter during the merger and ringdown is consistent with Λ as well. We performed 134 simulations where we systematically varied the equation of state as well as the mass ratio, neutron star mass, and aligned spin of the black hole. Using these simulations we develop an analytic representation of the full inspiral-merger-ringdown waveform calibrated to these numerical waveforms; we use this analytic waveform and a Fisher matrix analysis to estimate the accuracy to which Λ can be measured with gravitational-wave detectors. We find that although the inspiral tidal signal is small, coherently combining this signal with the merger-ringdown matter effect improves the measurability of Λ by a factor of ˜3 over using just the merger-ringdown matter effect alone. However, incorporating correlations between all the waveform parameters then decreases the measurability of Λ by a factor of ˜3. The uncertainty in Λ increases with the mass ratio, but decreases as the black hole spin increases. Overall, a single Advanced LIGO detector can only marginally measure Λ for mass ratios Q =2-5, black hole spins JBH/MBH2=-0.5-0.75, and neutron star masses MNS=1.2M⊙-1.45M⊙ at an optimally oriented distance of 100 Mpc. For the proposed Einstein Telescope, however, the uncertainty in Λ is an order of magnitude smaller.
Dust continuum spectra from model HII regions
NASA Technical Reports Server (NTRS)
Aannestad, P. A.; Emery, R. J.
1989-01-01
The infrared spectrum emitted by nebular dust, heated by the ionizing stars in H II blisters and spherical H II regions, is calculated for various model parameters. Absorption of the non-ionizing radiation in a neutral layer is included. Heating by the Lyman alpha photon field is taken into account. The dust is composed of silicate and graphite grains, and evaporation of the grains in the inner region is considered. The models are presented with a view to interpretation of infrared observations of dusty H II regions and can be applied directly to the infrared astronomy satellite survey data. The continuum emission is compared with calculated fine structure line emission.
Dust continuum spectra from model HII regions
NASA Technical Reports Server (NTRS)
Aannestad, P. A.; Emery, R. J.
1989-01-01
The infrared spectrum emitted by nebular dust, heated by the ionizing stars in H II blisters and spherical H II regions, is calculated for various model parameters. Absorption of the non-ionizing radiation in a neutral layer is included. Heating by the Lyman alpha photon field is taken into account. The dust is composed of silicate and graphite grains, and evaporation of the grains in the inner region is considered. The models are presented with a view to interpretation of infrared observations of dusty H II regions and can be applied directly to the infrared astronomy satellite survey data. The continuum emission is compared with calculated fine structure line emission.
EURO-CORDEX regional climate models: Performance over Mediterranean region
NASA Astrophysics Data System (ADS)
Stilinović, Tomislav; Güttler, Ivan; Srnec, Lidija; Branković, Čedo
2017-04-01
Regional climate models (RCMs) are high-resolution version of a global climate models (GCMs) designed to achieve simulations at horizontal resolutions relevant for human activities on local and regional spatial scales, and to simulate relevant processes in historical and potential future climate conditions. In this study, a set of experiments the EURO-CORDEX simulations are evaluated over the Mediterranean region. All simulations were made at the two horizontal resolutions (50 km and 12.5 km) and compared with gridded pan-European gridded dataset E-OBSv11 at the regular 0.25°×0.25° grid for the two periods (1989-2008 for the ERA-Interim-driven ensemble of simulations; 1971-2000 for the GCMs-driven ensemble of simulations). We will evaluate the impacts of (1) the boundary conditions, (2) different horizontal resolutions (0.44°/50 km vs. 0.11°/12.5 km), and (3) the impact of convective parametrization on systematic errors, specialy in case of the RegCM4 model extensively used at DHMZ. For each simulation commonly used evaluation metrics are applied. They include: (1) spatially-averaged differences between RCMs and observations, (2) the spatial 95 th percentiles of simulated and observed temperature and precipitation, (3) spatial correlation coefficients between models and observations, (4) the ratio of spatial standard deviations between simulated and observed fields, and (5) the Spearman rank correlations between simulated and observed time-series of spatially-averaged temperature and precipitation. As commonly found in other studies, the total precipitation in RCM simulations is often overestimated and spatial correlations are noticeably lower than for temperature. The results highlight that, the RegCM4 is able to capture the (observed) spatial variability of the Mediterranean temperature climate. This is indicated by high spatial correlations with values larger than 0.9 and values of normalized standard deviation below 1 for Mediterranean region. The results
Fluxon Modeling of Active Region Evolution
NASA Astrophysics Data System (ADS)
Deforest, C. E.; Kankelborg, C. C.; Davey, A. R.; Rachmeler, L.
2006-12-01
We present current results and status on fluxon modeling of free energy buildup and release in active regions. Our publicly available code, FLUX, has the unique ability to track magnetic energy buildup with a truly constrained topology in evolving, nonlinear force-free conditions. Recent work includes validation of the model against Low &Lou force-free field solutions, initial evolution studies of idealized active regions, and inclusion of locally parameterized reconnection into the model. FLUX is uniquely able to simulate complete active regions in 3-D on a single workstation; we estimate that a parallelized fluxon model, together with computer vision code to ingest solar data, could run faster than real time on a cluster of \\textasciitilde 30 CPUs and hence provide a true predictive space weather model in the style of predictive simulations of terrestrial weather.
Geopotential models in the Australian region
NASA Technical Reports Server (NTRS)
Kearsley, A. H. W.; Holloway, R. D.
1989-01-01
The ability of three high-order geopotential models (OSU81, GPM2 and OSU86E) to recover the gravity anomaly field (delta g) in the Australian region was tested. The region was divided into 2 x 2 deg blocks, and the mean and rms of the residual gravity (delta g measured - delta g modeled) was found to estimate the fit of the model to the point gravity data. The results showed that OSU81 and GPM2 performed similarly, recovering the delta g with a mean value of less than plus or minus 5 mGal in 63 and 70 percent of the blocks, respectively. However, both these models achieved a fit of worse that was plus or minus 13 mGal in 6 to 7 percent of cases. These were in areas either on or near the coast, or in the Central Australian region, inferring that for a precise geoid slope determination in these regions, a detailed analysis of delta g in region is needed. On the other hand, OSU86E produced a very good result, having a mean fit of less than plus or minus 5 mGal in 80 percent of the blocks, and worse than plus or minus 13 mGal in only 1 percent of cases. The rms values for this model were also improved over the other two models, indicating that for applications requiring highest precision, the preferred model is OSU86E.
Binary Black Holes: Mergers, Dynamics, and Waveforms
NASA Astrophysics Data System (ADS)
Centrella, Joan
2007-04-01
The final merger of two black holes is expected to be the strongest gravitational wave source for ground-based interferometers such as LIGO, VIRGO, and GEO600, as well as the space-based interferometer LISA. Observing these sources with gravitational wave detectors requires that we know the radiation waveforms they emit. Since these mergers take place in regions of extreme gravity, we need to solve Einstein's equations of general relativity on a computer in order to calculate these waveforms. For more than 30 years, scientists have tried to compute black hole mergers using the methods of numerical relativity. The resulting computer codes have been plagued by instabilities, causing them to crash well before the black holes in the binary could complete even a single orbit. Within the past few years, however, this situation has changed dramatically, with a series of remarkable breakthroughs. This talk will focus on new simulations that are revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, data analysis, and astrophysics.
Full Elastic Waveform Search Engine for Near Surface Imaging
NASA Astrophysics Data System (ADS)
Zhang, J.; Zhang, X.
2014-12-01
For processing land seismic data, the near-surface problem is often very complex and may severely affect our capability to image the subsurface. The current state-of-the-art technology for near surface imaging is the early arrival waveform inversion that solves an acoustic wave-equation problem. However, fitting land seismic data with acoustic wavefield is sometimes invalid. On the other hand, performing elastic waveform inversion is very time-consuming. Similar to a web search engine, we develop a full elastic waveform search engine that includes a large database with synthetic elastic waveforms accounting for a wide range of interval velocity models in the CMP domain. With each CMP gather of real data as an entry, the search engine applies Multiple-Randomized K-Dimensional (MRKD) tree method to find approximate best matches to the entry in about a second. Interpolation of the velocity models at CMP positions creates 2D or 3D Vp, Vs, and density models for the near surface area. The method does not just return one solution; it gives a series of best matches in a solution space. Therefore, the results can help us to examine the resolution and nonuniqueness of the final solution. Further, this full waveform search method can avoid the issues of initial model and cycle skipping that the method of full waveform inversion is difficult to deal with.
3-D crustal velocity structure of western Turkey: Constraints from full-waveform tomography
NASA Astrophysics Data System (ADS)
Çubuk-Sabuncu, Yeşim; Taymaz, Tuncay; Fichtner, Andreas
2017-09-01
The Sea of Marmara and western Turkey are characterized by intense seismicity and crustal deformation due to transition tectonics between the North Anatolian Fault Zone (NAFZ) and the extensional Aegean. Seismic imaging of the crust and uppermost mantle in W-NW Turkey is crucial to obtain a better understanding of its seismotectonics and geodynamics. So far, the Sea of Marmara and surroundings were considered in various active and passive seismic experiments providing significant information on crustal properties. Here, we further investigate the 3-D seismic velocity structure in this rapidly deforming region using non-linear full-waveform tomography based on the adjoint method. Our model is constrained by complete waveforms of 62 regional earthquakes (epicentral distance < 10°) with magnitudes Mw ≥ 3.7, which occurred between 2007 and 2015. Validation tests show that our final 3-D Earth model is able to explain seismic waveforms from earthquakes not used in the inversion at periods from 8-100 s to within the data uncertainties. Furthermore, quantitative resolution analyses yield 15 to 35 km horizontal resolution lengths in the shallow and deep crust beneath well-covered areas of W-NW Turkey. Our full-waveform tomography results indicate the presence of strong lateral and vertical velocity variations (2.55 ≤ VS ≤ 4.0 km/s) down to depths of ∼35 km. The seismic velocity distribution is characteristic of highly deformed and distributed crustal features along major fault zones (e.g. NAFZ and its branches), historic and recent regional volcanism (e.g. Kula volcanic province), and metamorphic core complex developments (e.g. Menderes and Kazdağ massifs). Radial anisotropy is very strong (around 20%) throughout the crust, further attesting to strong deformation and heterogeneity. Generally, our 3-D model is overall consistent with the active tectonics of western Turkey.
Hydrodynamical models of cometary H ii regions
NASA Astrophysics Data System (ADS)
Steggles, H. G.; Hoare, M. G.; Pittard, J. M.
2017-04-01
We have modelled the evolution of cometary H ii regions produced by zero-age main-sequence stars of O and B spectral types, which are driving strong winds and are born off-centre from spherically symmetric cores with power-law (α = 2) density slopes. A model parameter grid was produced that spans stellar mass, age and core density. Exploring this parameter space, we investigated limb-brightening, a feature commonly seen in cometary H ii regions. We found that stars with mass M⋆ ≥ 12 M⊙ produce this feature. Our models have a cavity bounded by a contact discontinuity separating hot shocked wind and ionized ambient gas that is similar in size to the surrounding H ii region. Because of early pressure confinement, we did not see shocks outside of the contact discontinuity for stars with M⋆ ≤ 40 M⊙, but the cavities were found to continue to grow. The cavity size in each model plateaus as the H ii region stagnates. The spectral energy distributions of our models are similar to those from identical stars evolving in uniform density fields. The turn-over frequency is slightly lower in our power-law models as a result of a higher proportion of low-density gas covered by the H ii regions.
2017 Regional, State, and Local Modelers' Workshop
The 2017 Regional, State, and Local (RSL) Modelers' Workshop is being held at the EPA's RTP, NC Campus on Monday, September 25th and Tuesday, September 26th, 2017.This page provides information on the agenda and registration for the RSL Modelers' Workshop.
NASA Astrophysics Data System (ADS)
Kurtz, N. T.; Galin, N.; Studinger, M.
2014-01-01
We develop an empirical model capable of simulating the mean echo power cross product of CryoSat-2 SAR and SARIn mode waveforms over sea ice covered regions. The model simulations are used to show the importance of variations in the radar backscatter coefficient with incidence angle and surface roughness for the retrieval of surface elevation of both sea ice floes and leads. The numerical model is used to fit CryoSat-2 waveforms to enable retrieval of surface elevation through the use of look-up tables and a bounded trust region Newton least squares fitting approach. The use of a model to fit returns from sea ice regions offers advantages over currently used threshold retracking methods which are here shown to be sensitive to the combined effect of bandwidth limited range resolution and surface roughness variations. Laxon et al. (2013) have compared ice thickness results from CryoSat-2 and IceBridge, and found good agreement, however consistent assumptions about the snow depth and density of sea ice were not used in the comparisons. To address this issue, we directly compare ice freeboard and thickness retrievals from the waveform fitting and threshold tracker methods of CryoSat-2 to Operation IceBridge data using a consistent set of parameterizations. For three IceBridge campaign periods from March 2011-2013, mean differences (CryoSat-2 - IceBridge) of 0.144 m and 1.351 m are respectively found between the freeboard and thickness retrievals using a 50% sea ice floe threshold retracker, while mean differences of 0.019 m and 0.182 m are found when using the waveform fitting method. This suggests the waveform fitting technique is capable of better reconciling the sea ice thickness data record from laser and radar altimetry data sets through the usage of consistent physical assumptions.
NASA Astrophysics Data System (ADS)
Chi, Wu-Cheng
This study used (1) 132-channel reflection profiles, forward gravity modeling, and (2) finite source inversions of earthquakes to analyze crustal evolution from Subduction to collision in the region of Taiwan. Reflection and gravity data in the offshore region shows that the accretionary prism in the Subduction zone is mainly sedimentary; however, due to tectonic wedging in the initial collision zone, high-density basement materials are incorporated into the rear of the accretionary prism and may extend northward to compose a portion of high-density rocks that underly southeastern Taiwan. Further to the north in the mature collision zone was the site of the 1999, Chi-Chi, Taiwan earthquake. For this earthquake and its large aftershocks, we inverted strong motion data for finite source processes to study the deep fault structures. The mainshock ruptured on a shallow eastward-dipping fault possibly rooted in the proposed decollement of thin-skin deformation model. Several aftershocks either nucleated in or ruptured the basement indicating active deformation below the decollement, suggesting basement-involved deformation. Interpreting finite-source results requires a thorough understanding of the uncertainty in the parameters. Further more, near-realtime applications of finite-source inversions for estimation of near-fault strong ground motion requires well constrained fault orientation and hypocentral parameters. With this in mind, we tested a wide range of hypocenters and focal mechanisms, and the corresponding fits of the synthetics to the observed waveforms when studying the aftershock source parameters. As a result, we obtained optimal waveform fits and determined how the errors reported in hypocenters and focal mechanisms affected the inverted waveforms and the sensitivity of the waveform fits. For example, if the hypocenter was within 5 km of the optimal hypocenter and the focal mechanism was within 20 degrees of optimal strike, dip, and rake, the waveform fits
NASA Astrophysics Data System (ADS)
Zhang, Xiaowen; Wang, Kaizhi; Liu, Xingzhao
2017-01-01
We investigate optimal waveform design using fractional Fourier transform in signal-dependent interference, as well as additive channel noise for stochastic extended target. Within constraints on waveform energy and bandwidth, optimal waveform design in fractional Fourier domain based on the signal-to-interference-plus-noise ratio criterion, probability of detection criterion, and mutual information criterion are modeled, respectively. In addition, the relationship between the optimal waveforms that are designed based on the three criteria is discussed. Simulations are conducted to illustrate that for all of the three criteria, the energy of optimal waveform can be distributed in some narrow bands where the target power is large and the interference power is small in fractional Fourier domain. Finally, the fractional Fourier domain waveform design method is proved more flexible and effective than traditional Fourier domain waveform design method, especially when the spectral density of target response and interference are relatively dispersed and flat.
Gold - A novel deconvolution algorithm with optimization for waveform LiDAR processing
NASA Astrophysics Data System (ADS)
Zhou, Tan; Popescu, Sorin C.; Krause, Keith; Sheridan, Ryan D.; Putman, Eric
2017-07-01
Waveform Light Detection and Ranging (LiDAR) data have advantages over discrete-return LiDAR data in accurately characterizing vegetation structure. However, we lack a comprehensive understanding of waveform data processing approaches under different topography and vegetation conditions. The objective of this paper is to highlight a novel deconvolution algorithm, the Gold algorithm, for processing waveform LiDAR data with optimal deconvolution parameters. Further, we present a comparative study of waveform processing methods to provide insight into selecting an approach for a given combination of vegetation and terrain characteristics. We employed two waveform processing methods: (1) direct decomposition, (2) deconvolution and decomposition. In method two, we utilized two deconvolution algorithms - the Richardson-Lucy (RL) algorithm and the Gold algorithm. The comprehensive and quantitative comparisons were conducted in terms of the number of detected echoes, position accuracy, the bias of the end products (such as digital terrain model (DTM) and canopy height model (CHM)) from the corresponding reference data, along with parameter uncertainty for these end products obtained from different methods. This study was conducted at three study sites that include diverse ecological regions, vegetation and elevation gradients. Results demonstrate that two deconvolution algorithms are sensitive to the pre-processing steps of input data. The deconvolution and decomposition method is more capable of detecting hidden echoes with a lower false echo detection rate, especially for the Gold algorithm. Compared to the reference data, all approaches generate satisfactory accuracy assessment results with small mean spatial difference (<1.22 m for DTMs, <0.77 m for CHMs) and root mean square error (RMSE) (<1.26 m for DTMs, <1.93 m for CHMs). More specifically, the Gold algorithm is superior to others with smaller root mean square error (RMSE) (<1.01 m), while the direct decomposition
Objective calibration of regional climate models
NASA Astrophysics Data System (ADS)
Bellprat, O.; Kotlarski, S.; Lüthi, D.; SchäR, C.
2012-12-01
Climate models are subject to high parametric uncertainty induced by poorly confined model parameters of parameterized physical processes. Uncertain model parameters are typically calibrated in order to increase the agreement of the model with available observations. The common practice is to adjust uncertain model parameters manually, often referred to as expert tuning, which lacks objectivity and transparency in the use of observations. These shortcomings often haze model inter-comparisons and hinder the implementation of new model parameterizations. Methods which would allow to systematically calibrate model parameters are unfortunately often not applicable to state-of-the-art climate models, due to computational constraints facing the high dimensionality and non-linearity of the problem. Here we present an approach to objectively calibrate a regional climate model, using reanalysis driven simulations and building upon a quadratic metamodel presented by Neelin et al. (2010) that serves as a computationally cheap surrogate of the model. Five model parameters originating from different parameterizations are selected for the optimization according to their influence on the model performance. The metamodel accurately estimates spatial averages of 2 m temperature, precipitation and total cloud cover, with an uncertainty of similar magnitude as the internal variability of the regional climate model. The non-linearities of the parameter perturbations are well captured, such that only a limited number of 20-50 simulations are needed to estimate optimal parameter settings. Parameter interactions are small, which allows to further reduce the number of simulations. In comparison to an ensemble of the same model which has undergone expert tuning, the calibration yields similar optimal model configurations, but leading to an additional reduction of the model error. The performance range captured is much wider than sampled with the expert-tuned ensemble and the presented
2011-09-01
DEVELOPING REGIONALIZED MODELS OF LITHOSPHERIC THICKNESS AND VELOCITY STRUCTURE ACROSS EURASIA AND THE MIDDLE EAST FROM JOINTLY INVERTING P-WAVE...09NA293221 and DE-AC52-07NA273442 Proposal No. BAA09-13 ABSTRACT The main goal of this project is to develop models of lithospheric velocity...of the lithosphere are key for accurately modeling not only travel times but also surface-wave dispersion velocities and full waveforms at regional
Advancements in Long-Offset Seismic Imaging: A Blind Test of Traveltime and Waveform Tomography
NASA Astrophysics Data System (ADS)
Zelt, C. A.; Pratt, G.; Brenders, A.; Hanson-Hedgecock, S.; Hole, J. A.
2005-05-01
In 2003 a realistic long-offset synthetic seismic dataset was made available to the community for the purpose of testing modelling, inversion and imaging algorithms. Here we present the results of 2-D traveltime and 2-D waveform tomography applied by workers who, at the time, did not know what the true model was. The synthetic wide-angle dataset consisting of 51 shots was calculated for a realistic crustal model using a 2-D visco-elastic code; these data are still available at terra.rice.edu/department/faculty/zelt/ccss/. The model is 250 km long, and the shot and receiver spacings are 5 km and 90 m, respectively. The center frequency of the source is 5 Hz, with energy between 2-11 Hz. The true model contains large-scale features such as laterally-varying sediment thickness, a basement outcrop, a low-velocity zone, and regions where the crust-mantle boundary is sharp and smooth. Superimposed on this are non-stationary intermediate to wavelength-scale stochastic features. Both first arrival and simultaneous PmP/Pn traveltime tomography were applied to obtain a smooth velocity model with a sharp Moho. The traveltime model compares favorably with the large-scale features of the true model, although it does not capture the details of the low-velocity zone or the smooth crust-mantle transition zone. However, the model obtained from first-arrival traveltime tomography was essential as a starting model for the 2-D acoustic, frequency-domain waveform tomography method we have applied. Data windowing in time, re-weighting in offset, and model smoothing were applied, and a relatively low starting frequency was used, 0.8 Hz, progressing up to 7 Hz. The final model from waveform tomography predicts the input data to a high degree of accuracy for each chosen frequency, and a comparison of the original time domain data with time-domain forward modelling through the final model also reveals a good match. The final model from waveform tomography matches the large and intermediate
Waveform design for detection of weapons based on signature exploitation
NASA Astrophysics Data System (ADS)
Ahmad, Fauzia; Amin, Moeness G.; Dogaru, Traian
2010-04-01
We present waveform design based on signature exploitation techniques for improved detection of weapons in urban sensing applications. A single-antenna monostatic radar system is considered. Under the assumption of exact knowledge of the target orientation and, hence, known impulse response, matched illumination approach is used for optimal target detection. For the case of unknown target orientation, we analyze the target signatures as random processes and perform signal-to-noise-ratio based waveform optimization. Numerical electromagnetic modeling is used to provide the impulse responses of an AK-47 assault rifle for various target aspect angles relative to the radar. Simulation results depict an improvement in the signal-to-noise-ratio at the output of the matched filter receiver for both matched illumination and stochastic waveforms as compared to a chirp waveform of the same duration and energy.
Frequency-domain ultrasound waveform tomography breast attenuation imaging
NASA Astrophysics Data System (ADS)
Sandhu, Gursharan Yash Singh; Li, Cuiping; Roy, Olivier; West, Erik; Montgomery, Katelyn; Boone, Michael; Duric, Neb
2016-04-01
Ultrasound waveform tomography techniques have shown promising results for the visualization and characterization of breast disease. By using frequency-domain waveform tomography techniques and a gradient descent algorithm, we have previously reconstructed the sound speed distributions of breasts of varying densities with different types of breast disease including benign and malignant lesions. By allowing the sound speed to have an imaginary component, we can model the intrinsic attenuation of a medium. We can similarly recover the imaginary component of the velocity and thus the attenuation. In this paper, we will briefly review ultrasound waveform tomography techniques, discuss attenuation and its relations to the imaginary component of the sound speed, and provide both numerical and ex vivo examples of waveform tomography attenuation reconstructions.
Xiang, J; Siddiqui, A H; Meng, H
2014-12-18
Due to the lack of patient-specific inlet flow waveform measurements, most computational fluid dynamics (CFD) simulations of intracranial aneurysms usually employ waveforms that are not patient-specific as inlet boundary conditions for the computational model. The current study examined how this assumption affects the predicted hemodynamics in patient-specific aneurysm geometries. We examined wall shear stress (WSS) and oscillatory shear index (OSI), the two most widely studied hemodynamic quantities that have been shown to predict aneurysm rupture, as well as maximal WSS (MWSS), energy loss (EL) and pressure loss coefficient (PLc). Sixteen pulsatile CFD simulations were carried out on four typical saccular aneurysms using 4 different waveforms and an identical inflow rate as inlet boundary conditions. Our results demonstrated that under the same mean inflow rate, different waveforms produced almost identical WSS distributions and WSS magnitudes, similar OSI distributions but drastically different OSI magnitudes. The OSI magnitude is correlated with the pulsatility index of the waveform. Furthermore, there is a linear relationship between aneurysm-averaged OSI values calculated from one waveform and those calculated from another waveform. In addition, different waveforms produced similar MWSS, EL and PLc in each aneurysm. In conclusion, inlet waveform has minimal effects on WSS, OSI distribution, MWSS, EL and PLc and a strong effect on OSI magnitude, but aneurysm-averaged OSI from different waveforms has a strong linear correlation with each other across different aneurysms, indicating that for the same aneurysm cohort, different waveforms can consistently stratify (rank) OSI of aneurysms.
Evaluation of regional-scale receptor modeling.
Lowenthal, Douglas H; Watson, John G; Koracin, Darko; Chen, L W Antony; Dubois, David; Vellore, Ramesh; Kumar, Naresh; Knipping, Eladio M; Wheeler, Neil; Craig, Kenneth; Reid, Stephen
2010-01-01
The ability of receptor models to estimate regional contributions to fine particulate matter (PM2.5) was assessed with synthetic, speciated datasets at Brigantine National Wildlife Refuge (BRIG) in New Jersey and Great Smoky Mountains National Park (GRSM) in Tennessee. Synthetic PM2.5 chemical concentrations were generated for the summer of 2002 using the Community Multiscale Air Quality (CMAQ) model and chemically speciated PM2.5 source profiles from the U.S. Environmental Protection Agency (EPA)'s SPECIATE and Desert Research Institute's source profile databases. CMAQ estimated the "true" contributions of seven regions in the eastern United States to chemical species concentrations and individual source contributions to primary PM2.5 at both sites. A seven-factor solution by the positive matrix factorization (PMF) receptor model explained approximately 99% of the variability in the data at both sites. At BRIG, PMF captured the first four major contributing sources (including a secondary sulfate factor), although diesel and gasoline vehicle contributions were not separated. However, at GRSM, the resolved factors did not correspond well to major PM2.5 sources. There were no correlations between PMF factors and regional contributions to sulfate at either site. Unmix produced five- and seven-factor solutions, including a secondary sulfate factor, at both sites. Some PMF factors were combined or missing in the Unmix factors. The trajectory mass balance regression (TMBR) model apportioned sulfate concentrations to the seven source regions using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) trajectories based on Meteorological Model Version 5 (MM5) and Eta Data Simulation System (EDAS) meteorological input. The largest estimated sulfate contributions at both sites were from the local regions; this agreed qualitatively with the true regional apportionments. Estimated regional contributions depended on the starting elevation of the trajectories and on
Waveform Modeling of the Crust and Upper Mantle Using S, Sp, SsPmP, and Shear-Coupled PL Waves
2008-05-10
standard error. Additionally, a significant variation in model parameters is not realistic given the tectonic and geologic setting of the regions...minimally affected by large-scale tectonic processes. However, a middle to lower crustal low- velocity zone obtained beneath all the seismic stations in the...region (Figures 5a–d), indicate possible local tectonic influences. Our estimate of crustal thickness beneath TAM (~36 km) is similar to that
Preconditioning Strategies in Elastic Full Waveform Inversion.
NASA Astrophysics Data System (ADS)
Matharu, G.; Sacchi, M. D.
2016-12-01
Elastic full waveform inversion (FWI) is inherently more non-linear than its acoustic counterpart, a property that stems from the increased model space of the problem. Whereas acoustic media can be parametrized by density and P-wave velocity, visco-elastic media are parametrized by density, attenuation and 21 independent coefficients of the elastic tensor. Imposing assumptions of isotropy and perfect elasticity to simplify the physics, reduces the number of independent parameters required to characterize a medium. Isotropic, elastic media can be parametrized in terms of density and the Lamé parameters. The different parameters can exhibit trade-off that manifest as attributes in the data. In the context of FWI, this means that certain parameters cannot be uniquely resolved. An ideal model update in full waveform inversion is equivalent to a Newton step. Explicit computation of the Hessian and its inverse is not computationally feasible in elastic FWI. The inverse Hessian scales the gradients to account for trade-off between parameters as well as compensating for inadequate illumination related to source-receiver coverage. Gradient preconditioners can be applied to mimic the action of the inverse Hessian and partially correct for inaccuracies in the gradient. In this study, we investigate the effects of model reparametrization by recasting a regularized form of the least-squares waveform misfit into a preconditioned formulation. New model parameters are obtained by applying invertible weighting matrices to the model vector. The weighting matrices are related to estimates of the prior model covariance matrix and incorporate information about spatially variant correlations of model parameters as well as correlations between independent parameters. We compare the convergence of conventional FWI to FWI after model reparametrization.
Full waveform inversion for ultrasonic flaw identification
NASA Astrophysics Data System (ADS)
Seidl, Robert; Rank, Ernst
2017-02-01
Ultrasonic Nondestructive Testing is concerned with detecting flaws inside components without causing physical damage. It is possible to detect flaws using ultrasound measurements but usually no additional details about the flaw like position, dimension or orientation are available. The information about these details is hidden in the recorded experimental signals. The idea of full waveform inversion is to adapt the parameters of an initial simulation model of the undamaged specimen by minimizing the discrepancy between these simulated signals and experimentally measured signals of the flawed specimen. Flaws in the structure are characterized by a change or deterioration in the material properties. Commonly, full waveform inversion is mostly applied in seismology on a larger scale to infer mechanical properties of the earth. We propose to use acoustic full waveform inversion for structural parameters to visualize the interior of the component. The method is adapted to US NDT by combining multiple similar experiments on the test component as the typical small amount of sensors is not sufficient for a successful imaging. It is shown that the combination of simulations and multiple experiments can be used to detect flaws and their position, dimension and orientation in emulated simulation cases.
On the accuracy and precision of numerical waveforms: effect of waveform extraction methodology
NASA Astrophysics Data System (ADS)
Chu, Tony; Fong, Heather; Kumar, Prayush; Pfeiffer, Harald P.; Boyle, Michael; Hemberger, Daniel A.; Kidder, Lawrence E.; Scheel, Mark A.; Szilagyi, Bela
2016-08-01
We present a new set of 95 numerical relativity simulations of non-precessing binary black holes (BBHs). The simulations sample comprehensively both black-hole spins up to spin magnitude of 0.9, and cover mass ratios 1-3. The simulations cover on average 24 inspiral orbits, plus merger and ringdown, with low initial orbital eccentricities e\\lt {10}-4. A subset of the simulations extends the coverage of non-spinning BBHs up to mass ratio q = 10. Gravitational waveforms at asymptotic infinity are computed with two independent techniques: extrapolation and Cauchy characteristic extraction. An error analysis based on noise-weighted inner products is performed. We find that numerical truncation error, error due to gravitational wave extraction, and errors due to the Fourier transformation of signals with finite length of the numerical waveforms are of similar magnitude, with gravitational wave extraction errors dominating at noise-weighted mismatches of ˜ 3× {10}-4. This set of waveforms will serve to validate and improve aligned-spin waveform models for gravitational wave science.
A Time Domain Waveform for Testing General Relativity
NASA Astrophysics Data System (ADS)
Huwyler, Cédric; Porter, Edward K.; Jetzer, Philippe
2015-05-01
Gravitational-wave parameter estimation is only as good as the theory the waveform generation models are based upon. It is therefore crucial to test General Relativity (GR) once data becomes available. Many previous works, such as studies connected with the ppE framework by Yunes and Pretorius, rely on the stationary phase approximation (SPA) to model deviations from GR in the frequency domain. As Fast Fourier Transform algorithms have become considerably faster and in order to circumvent possible problems with the SPA, we test GR with corrected time domain waveforms instead of SPA waveforms. Since a considerable amount of work has been done already in the field using SPA waveforms, we establish a connection between leading-order-corrected waveforms in time and frequency domain, concentrating on phase-only corrected terms. In a Markov Chain Monte Carlo study, whose results are preliminary and will only be available later, we will assess the ability of the eLISA detector to measure deviations from GR for signals coming from supermassive black hole inspirals using these corrected waveforms.
AIR QUALITY MODELING OF AMMONIA: A REGIONAL MODELING PERSPECTIVE
The talk will address the status of modeling of ammonia from a regional modeling perspective, yet the observations and comments should have general applicability. The air quality modeling system components that are central to modeling ammonia will be noted and a perspective on ...
Full Seismic Waveform Inversion for the Japanese Islands
NASA Astrophysics Data System (ADS)
Žukauskaitė, Saulė; Steptoe, Hamish; Fichtner, Andreas
2015-04-01
We present a seismic tomography model for the Japanese archipelago obtained using full waveform inversion and adjoint methods. A credible seismic velocity model is essential for the Japan region as a means to further our understanding of earthquake source mechanics by allowing for more accurate seismic source inversion, to benefit seismic hazard assessment as well as early warning systems, and to comprehend the complexity of the tectonic setting. The study area covers the Japanese islands, Taiwan, Korean peninsula, easternmost parts of China and Russia, Sakhalin and the majority of the Kuril Islands chain. The domain extends down into the mantle transition zone. We choose 58 earthquakes of magnitudes Mw5.0 - 6.9 distributed across the model domain as uniformly as possible. The data are obtained from several seismic networks in the area, namely F-net in Japan, BATS in Taiwan, South Korean National Earthquake Network and several stations from each China National Seismic Network, New China Digital Seismograph Network, Global Seismograph Network and Korean Seismic Network made available by IRIS Data Management Center. To facilitate full waveform inversion the forward problem is solved numerically using the spectral element method (SEM), which comes with the geometric flexibility of the finite-elements method and the accuracy of the spectral methods. Owing to the SEM and the advance in High Performance Computing we are able to perform numerical simulations of seismic waves in realistic 3D heterogeneous visco-elastic structures. Differences between the calculated and the real waveforms are quantified using the time-frequency misfits (Fichtner et al., 2008), which allow us to explore the temporal evolution of the frequency content of the data with no need to identify specific seismic phases. We use adjoint methods as an effective means to obtain sensitivity kernels and ultimately gradients, required for iterative gradient-based minimisation techniques. The obtained model
Processing Aftershock Sequences Using Waveform Correlation
NASA Astrophysics Data System (ADS)
Resor, M. E.; Procopio, M. J.; Young, C. J.; Carr, D. B.
2008-12-01
For most event monitoring systems, the objective is to keep up with the flow of incoming data, producing a bulletin with some modest, relatively constant, time delay after present time, often a period of a few hours or less. Because the association problem scales exponentially and not linearly with the number of detections, a dramatic increase in seismicity due to an aftershock sequence can easily cause the bulletin delay time to increase dramatically. In some cases, the production of a bulletin may cease altogether, until the automatic system can catch up. For a nuclear monitoring system, the implications of such a delay could be dire. Given the expected similarity between a mainshock and aftershocks, it has been proposed that waveform correlation may provide a powerful means to simultaneously increase the efficiency of processing aftershock sequences, while also lowering the detection threshold and improving the quality of the event solutions. However, many questions remain unanswered. What are the key parameters for achieving the best correlations between waveforms (window length, filtering, etc.), and are they sequence-dependent? What is the overall percentage of similar events in an aftershock sequence, i.e. what is the maximum level of efficiency that a waveform correlation could be expected to achieve? Finally, how does this percentage of events vary among sequences? Using data from the aftershock sequence for the December 26, 2004 Mw 9.1 Sumatra event, we investigate these issues by building and testing a prototype waveform correlation event detection system that automatically expands its library of known events as new signatures are indentified in the aftershock sequence (by traditional signal detection and event processing). Our system tests all incoming data against this dynamic library, thereby identify any similar events before traditional processing takes place. In the region surrounding the Sumatra event, the NEIC EDR contains 4997 events in the 9
Model Effects on GLAS-Based Regional Estimates of Forest Biomass and Carbon
NASA Technical Reports Server (NTRS)
Nelson, Ross
2008-01-01
ICESat/GLAS waveform data are used to estimate biomass and carbon on a 1.27 million sq km study area. the Province of Quebec, Canada, below treeline. The same input data sets and sampling design are used in conjunction with four different predictive models to estimate total aboveground dry forest biomass and forest carbon. The four models include nonstratified and stratified versions of a multiple linear model where either biomass or (square root of) biomass serves as the dependent variable. The use of different models in Quebec introduces differences in Provincial biomass estimates of up to 0.35 Gt (range 4.942+/-0.28 Gt to 5.29+/-0.36 Gt). The results suggest that if different predictive models are used to estimate regional carbon stocks in different epochs, e.g., y2005, y2015, one might mistakenly infer an apparent aboveground carbon "change" of, in this case, 0.18 Gt, or approximately 7% of the aboveground carbon in Quebec, due solely to the use of different predictive models. These findings argue for model consistency in future, LiDAR-based carbon monitoring programs. Regional biomass estimates from the four GLAS models are compared to ground estimates derived from an extensive network of 16,814 ground plots located in southern Quebec. Stratified models proved to be more accurate and precise than either of the two nonstratified models tested.
Model Effects on GLAS-Based Regional Estimates of Forest Biomass and Carbon
NASA Technical Reports Server (NTRS)
Nelson, Ross
2008-01-01
ICESat/GLAS waveform data are used to estimate biomass and carbon on a 1.27 million sq km study area. the Province of Quebec, Canada, below treeline. The same input data sets and sampling design are used in conjunction with four different predictive models to estimate total aboveground dry forest biomass and forest carbon. The four models include nonstratified and stratified versions of a multiple linear model where either biomass or (square root of) biomass serves as the dependent variable. The use of different models in Quebec introduces differences in Provincial biomass estimates of up to 0.35 Gt (range 4.942+/-0.28 Gt to 5.29+/-0.36 Gt). The results suggest that if different predictive models are used to estimate regional carbon stocks in different epochs, e.g., y2005, y2015, one might mistakenly infer an apparent aboveground carbon "change" of, in this case, 0.18 Gt, or approximately 7% of the aboveground carbon in Quebec, due solely to the use of different predictive models. These findings argue for model consistency in future, LiDAR-based carbon monitoring programs. Regional biomass estimates from the four GLAS models are compared to ground estimates derived from an extensive network of 16,814 ground plots located in southern Quebec. Stratified models proved to be more accurate and precise than either of the two nonstratified models tested.
Observation simulation experiments with regional prediction models
NASA Technical Reports Server (NTRS)
Diak, George; Perkey, Donald J.; Kalb, Michael; Robertson, Franklin R.; Jedlovec, Gary
1990-01-01
Research efforts in FY 1990 included studies employing regional scale numerical models as aids in evaluating potential contributions of specific satellite observing systems (current and future) to numerical prediction. One study involves Observing System Simulation Experiments (OSSEs) which mimic operational initialization/forecast cycles but incorporate simulated Advanced Microwave Sounding Unit (AMSU) radiances as input data. The objective of this and related studies is to anticipate the potential value of data from these satellite systems, and develop applications of remotely sensed data for the benefit of short range forecasts. Techniques are also being used that rely on numerical model-based synthetic satellite radiances to interpret the information content of various types of remotely sensed image and sounding products. With this approach, evolution of simulated channel radiance image features can be directly interpreted in terms of the atmospheric dynamical processes depicted by a model. Progress is being made in a study using the internal consistency of a regional prediction model to simplify the assessment of forced diabatic heating and moisture initialization in reducing model spinup times. Techniques for model initialization are being examined, with focus on implications for potential applications of remote microwave observations, including AMSU and Special Sensor Microwave Imager (SSM/I), in shortening model spinup time for regional prediction.
NASA Astrophysics Data System (ADS)
TAO, K.; Grand, S.; Niu, F.; Chen, M.; Zhu, H.
2015-12-01
Northeast China has undergone widespread extension and magmatism since Late Cretaceous. There are many Cenozoic volcanoes in this region and a few of them are still active today, such as Changbaishan and Wudalianchi. Previous tomography models show stagnant slabs within the transition zone beneath NE China, and suggest deep slab control on the regional tectonics and volcanism. Proposed mechanisms for the magmatism include: 1) a mantle plume, 2) hot upwelling above the stagnant slab by deep dehydration and 3) upwelling induced by deep slab segmentation and detachment. To date, NE China seismic images still contain enough uncertainty to allow for multiple models. Using the dense seismic data coverage in NE China and adjacent regions our goal is to make high-resolution image of the transition zone and slab structure to test the origins of intraplate volcanism. Recently Chen et al. (2015) developed a 3D model for P and S velocity structure beneath East Asia using adjoint tomography using the SPECFEM3D synthetic technique and cross-correlation time shifts as the objective function. We use their model as a starting model and further improve the resolution by fitting waveforms to a shorter period (from ~12s to ~5s) using the correlation coefficient as the objective function. The new objective function is closely related to the L2 waveform misfit but is insensitive to a constant amplitude ratio between the synthetic and data within each time window used. This feature is desirable because the absolute amplitude can be hard to model as it can be affected by many factors difficult to incorporate in simulations, such as site effects, source magnitude and mechanism error or even poor calibration of instruments. During inversion we focus specifically on the transition zone and the structure of slabs with the goal of fitting triplicated and multipath body waves. We have performed a waveform inversion experiment using data from a single deep earthquake. Excellent fits of the
REGIONAL SEISMIC AMPLITUDE MODELING AND TOMOGRAPHY FOR EARTHQUAKE-EXPLOSION DISCRIMINATION
Walter, W R; Pasyanos, M E; Matzel, E; Gok, R; Sweeney, J; Ford, S R; Rodgers, A J
2008-07-08
We continue exploring methodologies to improve earthquake-explosion discrimination using regional amplitude ratios such as P/S in a variety of frequency bands. Empirically we demonstrate that such ratios separate explosions from earthquakes using closely located pairs of earthquakes and explosions recorded on common, publicly available stations at test sites around the world (e.g. Nevada, Novaya Zemlya, Semipalatinsk, Lop Nor, India, Pakistan, and North Korea). We are also examining if there is any relationship between the observed P/S and the point source variability revealed by longer period full waveform modeling (e. g. Ford et al 2008). For example, regional waveform modeling shows strong tectonic release from the May 1998 India test, in contrast with very little tectonic release in the October 2006 North Korea test, but the P/S discrimination behavior appears similar in both events using the limited regional data available. While regional amplitude ratios such as P/S can separate events in close proximity, it is also empirically well known that path effects can greatly distort observed amplitudes and make earthquakes appear very explosion-like. Previously we have shown that the MDAC (Magnitude Distance Amplitude Correction, Walter and Taylor, 2001) technique can account for simple 1-D attenuation and geometrical spreading corrections, as well as magnitude and site effects. However in some regions 1-D path corrections are a poor approximation and we need to develop 2-D path corrections. Here we demonstrate a new 2-D attenuation tomography technique using the MDAC earthquake source model applied to a set of events and stations in both the Middle East and the Yellow Sea Korean Peninsula regions. We believe this new 2-D MDAC tomography has the potential to greatly improve earthquake-explosion discrimination, particularly in tectonically complex regions such as the Middle East. Monitoring the world for potential nuclear explosions requires characterizing seismic
An ionization region model of the reactive Ar/O2 high power impulse magnetron sputtering discharge
NASA Astrophysics Data System (ADS)
Gudmundsson, Jon Tomas; Lundin, Daniel; Brenning, Nils; Raadu, Michel A.; Huo, Chunqing; Minea, Tiberiu
2016-09-01
A reactive ionization region model (R-IRM) is developed to describe the reactive Ar/O2 high power impulse magnetron sputtering (HiPIMS) discharge with titanium target. We compare the discharge properties when the discharge is operated in the two well established operating modes, the metal mode and the poisoned mode. Experimentally, it is found that in the metal mode the discharge current waveform displays a typical non-reactive evolution, while in the poisoned mode the discharge current waveform becomes distinctly triangular and the current increases significantly. Using the R-IRM we find that when the discharge is operated in the metal mode Ar+ and Ti+-ions contribute most significantly (roughly equal amounts) to the discharge current while in the poisoned mode the Ar+-ions contribute most significantly to the discharge current while the contribution of O+-ions and secondary electron emission is much smaller. Furthermore, we find that recycling of ionized atoms coming from the target are required for the current generation in both modes of operation. In the metal mode self-sputter recycling dominates and in the poisoned mode working gas recycling dominates, and it is concluded that the dominating type of recycling determines the discharge current waveform.
Hook Region Represented in a Cochlear Model
NASA Astrophysics Data System (ADS)
Steele, Charles R.; Kim, Namkeun; Puria, Sunil
2009-02-01
The present interest is in discontinuities. Particularly the geometry of the hook region, with the flexible round window nearly parallel with the basilar membrane, is not represented by a standard box model, in which both stapes and round window are placed at the end. A better model represents the round window by a soft membrane in the wall of scala tympani, with the end closed. This complicates the analysis considerably. Features are that the significant compression wave, i.e., the fast wave, is of negligible magnitude in this region, and that significant evanescent waves occur because of the discontinuities at the beginning and end of the simulated round window. The effect of this on both high frequency, with maximum basilar membrane response in the hook region, and lower frequencies are determined.
Regional Models for Sediment Toxicity Assessment
This paper investigates the use of empirical models to predict the toxicity of sediment samples within a region to laboratory test organisms based on sediment chemistry. In earlier work, we used a large nationwide database of matching sediment chemistry and marine amphipod sedim...
Regional Models for Sediment Toxicity Assessment
This paper investigates the use of empirical models to predict the toxicity of sediment samples within a region to laboratory test organisms based on sediment chemistry. In earlier work, we used a large nationwide database of matching sediment chemistry and marine amphipod sedim...
Talker identification from analysis of raw complex waveforms
NASA Astrophysics Data System (ADS)
Stokes, Michael A.
2002-05-01
Stokes (1996) demonstrated that visual inspection of raw complex waveforms can be used to identify a vowel produced by a talker. This research resulted in the MAS Model of Vowel Perception and Production (Stokes, 1998; http://home.indy.net/~masmodel/). More recently, another experiment extended this work to female talkers as well as male talkers (Stokes, 2001). Together, this research represents the only ongoing comprehensive research involving visual inspection of raw complex waveforms for identifying vowels produced by any talker. As an extension of the work, the present study involves identifying a talker from a waveform display. Unique voice signatures identified from waveform displays are used to identify a talker from a set of 10 talkers in the same way as one would identify a person from fingerprints. In two trials (the word who'd in trial 1 and heed in trial 2), a talker was correctly identified from a set of 10 unique talkers per trial using small visual samples of waveforms and matching it to a waveform sample of the talkers to be identified.
Design and Testing of Space Telemetry SCA Waveform
NASA Technical Reports Server (NTRS)
Mortensen, Dale J.; Handler, Louis M.; Quinn, Todd M.
2006-01-01
A Software Communications Architecture (SCA) Waveform for space telemetry is being developed at the NASA Glenn Research Center (GRC). The space telemetry waveform is implemented in a laboratory testbed consisting of general purpose processors, field programmable gate arrays (FPGAs), analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). The radio hardware is integrated with an SCA Core Framework and other software development tools. The waveform design is described from both the bottom-up signal processing and top-down software component perspectives. Simulations and model-based design techniques used for signal processing subsystems are presented. Testing with legacy hardware-based modems verifies proper design implementation and dynamic waveform operations. The waveform development is part of an effort by NASA to define an open architecture for space based reconfigurable transceivers. Use of the SCA as a reference has increased understanding of software defined radio architectures. However, since space requirements put a premium on size, mass, and power, the SCA may be impractical for today s space ready technology. Specific requirements for an SCA waveform and other lessons learned from this development are discussed.
Compression strategies for LiDAR waveform cube
NASA Astrophysics Data System (ADS)
Jóźków, Grzegorz; Toth, Charles; Quirk, Mihaela; Grejner-Brzezinska, Dorota
2015-01-01
Full-waveform LiDAR data (FWD) provide a wealth of information about the shape and materials of the surveyed areas. Unlike discrete data that retains only a few strong returns, FWD generally keeps the whole signal, at all times, regardless of the signal intensity. Hence, FWD will have an increasingly well-deserved role in mapping and beyond, in the much desired classification in the raw data format. Full-waveform systems currently perform only the recording of the waveform data at the acquisition stage; the return extraction is mostly deferred to post-processing. Although the full waveform preserves most of the details of the real data, it presents a serious practical challenge for a wide use: much larger datasets compared to those from the classical discrete return systems. Atop the need for more storage space, the acquisition speed of the FWD may also limit the pulse rate on most systems that cannot store data fast enough, and thus, reduces the perceived system performance. This work introduces a waveform cube model to compress waveforms in selected subsets of the cube, aimed at achieving decreased storage while maintaining the maximum pulse rate of FWD systems. In our experiments, the waveform cube is compressed using classical methods for 2D imagery that are further tested to assess the feasibility of the proposed solution. The spatial distribution of airborne waveform data is irregular; however, the manner of the FWD acquisition allows the organization of the waveforms in a regular 3D structure similar to familiar multi-component imagery, as those of hyper-spectral cubes or 3D volumetric tomography scans. This study presents the performance analysis of several lossy compression methods applied to the LiDAR waveform cube, including JPEG-1, JPEG-2000, and PCA-based techniques. Wide ranges of tests performed on real airborne datasets have demonstrated the benefits of the JPEG-2000 Standard where high compression rates incur fairly small data degradation. In
NASA Astrophysics Data System (ADS)
Konca, A.
2013-12-01
A kinematic model for the Mw7.1 2011 Van Earthquake was obtained using regional, teleseismic and GPS data. One issue regarding regional data is that 1D Green's functions may not be appropriate due to complications in the upper mantle and crust that affects the Pnl waveforms. In order to resolve whether the 1D Green's function is appropriate, an aftershock of the main event was also modeled, which is then used as a criterion in the selection of the regional stations. The GPS data itself is not sufficient to obtain a slip model, but helps constrain the slip distribution. The slip distribution is up-dip and bilateral with more slip toward west, where the maximum slip reaches 4 meters. The rupture velocity is about 1.5 km/s.
Full Seismic Waveform Inversion for the Japanese Islands
NASA Astrophysics Data System (ADS)
Žukauskaitė, S.; Steptoe, H.; Fichtner, A.
2014-12-01
We present a seismic tomography model for the Japanese archipelago obtained using full waveform inversion and adjoint methods. A credible seismic velocity model is essential for the Japan region as a means to comprehend the complexity of the tectonic setting, further our understanding of earthquake source mechanics and benefit seismic hazard assessment as well as early warning systems. The study area covers the Japanese islands, Taiwan, Korean peninsula, easternmost parts of China and Russia, Sakhalin and the majority of the Kuril Islands chain. The domain extends down into the mantle transition zone. We choose 58 earthquakes of magnitudes Mw5.0 - 6.9 distributed across the model domain as uniformly as possible. The data are obtained from several seismic networks in the area, namely F-net in Japan, BATS in Taiwan, South Korean National Earthquake Network and several stations from each China National Seismic Network, New China Digital Seismograph Network, Global Seismograph Network and Korean Seismic Network made available by IRIS Data Management Center. To facilitate full waveform inversion we use the spectral element method (SEM), which comes with the geometric flexibility of the finite-elements method and the accuracy of the spectral methods. Owing to the SEM and the advance in High Performance Computing we are able to perform numerical simulations of seismic waves in realistic 3D heterogeneous visco-elastic structures. Differences between the calculated and the real waveforms are quantified using the time-frequency misfits (Fichtner et al., 2008), which allow us to explore the temporal evolution of the frequency content of the data with no need to identify specific seismic phases. We use adjoint methods as an effective means to obtain sensitivity kernels and ultimately gradients, required for iterative gradient-based minimisation techniques. With such a methodology we are able to explain the data of dominant period as low as 10 s. The final results of this study
Shallow oceanic crust: Full waveform tomographic images of the seismic layer 2A/2B boundary
NASA Astrophysics Data System (ADS)
Christeson, Gail L.; Morgan, Joanna V.; Warner, Michael R.
2012-05-01
We present results of full-waveform tomographic inversions of four profiles acquired over young intermediate- and fast spreading rate oceanic crust. The mean velocity-depth functions from our study include a 0.25-0.30 km-thick low-velocity, low-gradient region beneath the seafloor overlying a 0.24-0.28-km-thick high-gradient region; together these regions compose seismic layer 2A. Mean layer 2A interval velocities are 3.0-3.2 km/s. The mean depth to the layer 2A/2B boundary is 0.49-0.54 km, and mean velocities within the upper 0.25 km of layer 2B are 4.7-4.9 km/s. Previous velocity analyses of the study areas using 1-D ray tracing underestimate the thickness of the high-gradient region at the base of layer 2A. We observe differences in the waveform inversion velocity models that correspond to imaging of the layer 2A event; regions with a layer 2A event have higher velocity gradients at the base of layer 2A. Intermittent high velocities, which we interpret as massive flows, are observed in the waveform inversion velocity models at 0.05-0.10 km below the seafloor (bsf) over 10-25% of the intermediate-spreading profiles and 20-45% of the fast spreading profiles. The high-gradient region located 0.25-0.54 km bsf at the base of layer 2A may be associated with an increased prevalence of massive flows, the first appearance of dikes (lava-dike transition zone), or with increased crack sealing by hydrothermal products. The upper portion of layer 2B, which begins at 0.49-0.54 km bsf, may correspond to sheeted dikes or the top of the transition zone of lavas and dikes.
Gao, Mingwu; Rose, William C; Fetics, Barry; Kass, David A; Chen, Chen-Huan; Mukkamala, Ramakrishna
2016-09-14
Generalized transfer functions (GTFs) are available to compute the more relevant central blood pressure (BP) waveform from a more easily measured radial BP waveform. However, GTFs are population averages and therefore may not adapt to variations in pulse pressure (PP) amplification (ratio of radial to central PP). A simple adaptive transfer function (ATF) was developed. First, the transfer function is defined in terms of the wave travel time and reflection coefficient parameters of an arterial model. Then, the parameters are estimated from the radial BP waveform by exploiting the observation that central BP waveforms exhibit exponential diastolic decays. The ATF was assessed using the original data that helped popularize the GTF. These data included radial BP waveforms and invasive reference central BP waveforms from cardiac catheterization patients. The data were divided into low, middle, and high PP amplification groups. The ATF estimated central BP with greater accuracy than GTFs in the low PP amplification group (e.g., central systolic BP and PP root-mean-square-errors of 3.3 and 4.2 mm Hg versus 6.2 and 7.1 mm Hg; p ≤ 0.05) while showing similar accuracy in the higher PP amplification groups. The ATF may permit more accurate, non-invasive central BP monitoring in elderly and hypertensive patients.
Gao, Mingwu; Rose, William C.; Fetics, Barry; Kass, David A.; Chen, Chen-Huan; Mukkamala, Ramakrishna
2016-01-01
Generalized transfer functions (GTFs) are available to compute the more relevant central blood pressure (BP) waveform from a more easily measured radial BP waveform. However, GTFs are population averages and therefore may not adapt to variations in pulse pressure (PP) amplification (ratio of radial to central PP). A simple adaptive transfer function (ATF) was developed. First, the transfer function is defined in terms of the wave travel time and reflection coefficient parameters of an arterial model. Then, the parameters are estimated from the radial BP waveform by exploiting the observation that central BP waveforms exhibit exponential diastolic decays. The ATF was assessed using the original data that helped popularize the GTF. These data included radial BP waveforms and invasive reference central BP waveforms from cardiac catheterization patients. The data were divided into low, middle, and high PP amplification groups. The ATF estimated central BP with greater accuracy than GTFs in the low PP amplification group (e.g., central systolic BP and PP root-mean-square-errors of 3.3 and 4.2 mm Hg versus 6.2 and 7.1 mm Hg; p ≤ 0.05) while showing similar accuracy in the higher PP amplification groups. The ATF may permit more accurate, non-invasive central BP monitoring in elderly and hypertensive patients. PMID:27624389
Sandia's Arbitrary Waveform MEMO Actuator
Brian Sosnowchik, Mark Jenkins
2003-08-07
SAMA is a multichannel, arbitrary waveform generator program for driving microelectromechanical systems (MEMS). It allows the user to piece together twelve available wave parts, thereby permitting the user to create practically any waveform, or upload a previously constructed signal. The waveforms (bundled together as a signal) may simultaneously be output through four different channels to actuate MEMS devices, and the number of output channels may be increased depending on the DAQ card or instrument utilized. Additionally, real-time changes may be made to the frequency and amplitude. The signal may be paused temporarily. The waveform may be saved to file for future uploading. Recent work for this version has focused on modifications that will allow loading previously generated arbitrary waveforms, independent channel waveform amplification, adding a pause function, separating the "modify waveform: and "end program" functions, and simplifying the user interface by adding test blocks with statements to help the user program and output the desired signals. The program was developed in an effort to alleviate some of the limitations of Micro Driver. For example, Micro Driver will not allow the user to select a segment of a sine wave, but rather the user is limited to choosing either a whole or half sine wave pattern. It therefore becomes quite difficult ot construct partial sine wave patterns out of a "ramp" waveparts for several reasons. First, one must determine on paper how many data points each ramp will cover, and what the slopes of these ramps will be. Second, from what was observed, Micro Driver has difficulty processing more than six distinct waveparts during sequencing. The program will allow the user to input the various waves into the desired sequence; however, it will not allow the user to compile them (by clicking "ok" and returning to the main screen). Third, should the user decide that they want to increase the amplitute of the output signal, they must
Progress towards regional flash flood modelling
NASA Astrophysics Data System (ADS)
Bates, P. D.; Coxon, G.; Quinn, N.; Freer, J. E.
2015-12-01
Flash flooding causes widespread disruption and damage across the UK, with recent research indicating that the occurrence and severity of intense rainfall is likely to increase in the future. To date, our ability to model such events at anything other than local scales has been hindered both by a lack of data at adequate spatial and temporal resolutions and a limited understanding of the processes involved in flooding from short duration, high intensity rainfall events. To enable effective flood risk management and decisions, it is essential that we improve our understanding of the variability in risk from such events across the UK and this requires an ability to undertake flash flood modelling at regional scales. In this study, we have implemented a coupled hydrological - hydrodynamic model for the representation of flash flooding at regional scales over long durations. To provide inputs to these models, we have developed a gridded sub-daily (hourly) rainfall record of the UK from 1993 to 2011. This enables us to more accurately represent flooding resulting from short duration rainfall events that are poorly represented by commonly utilised daily rainfall data. For a given region of interest we cascade rainfall estimates from our sub-daily dataset into a semi-distributed hydrological model (Dynamic Topmodel) in order to generate river discharge estimates which are then used to force a widely utilised inundation model (LISFLOOD-FP). Here we present the results from a test case in order to demonstrate the capabilities of the modelling framework over a variety of events with differing characteristics. The results will provide an insight into our capabilities of representing flash flooding and highlight key areas for future model development and enhanced process understanding.
Regional geoid height models developed using aerogravity
NASA Astrophysics Data System (ADS)
Roman, D. R.; Li, X.; Holmes, S. A.
2013-12-01
The techniques employed during the development of the Geoid Slope Validation Study of 2011 (GSVS 11) were adapted to modeling of regional geoid height models. Aerogravity from the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) Project was first evaluated with respect to satellite gravity field models developed from both GRACE and GOCE data to establish long wavelength consistency and remove biases in individual survey lines. In turn, the airborne and satellite gravity were then combined to evaluate surface gravity data from around 1400 separate surveys over the conterminous United States (CONUS). These surveys can span anywhere from 10's to 100's of kilometers and comprise the surface gravity database held by the U.S. National Geodetic Survey. These surface data have been used as-is in the development of previous gravimetric geoid models. With the availability of aerogravity, these surveys were examined to detect and mitigate potential biases that can create artifacts in geoid height models. About 5% of these surveys exhibit significant biases of 3-5 mGals, which equate to 10-20 cm errors in subsequent geoid height models. Given the requirement for cm-level accuracy in a future vertical datum based on geoid height models, these errors must be addressed. GSVS 11 demonstrated that it is possible to combine satellite, airborne and surface gravity to achieve cm-level accuracy over a limited locale. This study demonstrates that this can also be achieved over more regional scales. While not all of the CONUS has yet been flown by the GRAV-D Project, significant portions have been flown and those regions have been evaluated here. In the GSVS 11 study, external metrics were collected simultaneously to permit evaluation of the overall error. Such data is generally not available on a national basis, but comparisons are made with the GSVS 11 data, tidal benchmarks in combination with ocean topography models, and astrogeodetic deflection of the vertical
NASA Astrophysics Data System (ADS)
Fielding, E. J.; Lundgren, P.; Polet, J.; Taymaz, T.; Owen, S. E.; Simons, M.; Motagh, M.; Yun, S.
2012-12-01
A large Mw 7.1 earthquake struck the area north of the city of Van in eastern Turkey on 23 October 2011. The main shock epicenter and most of the aftershocks were located south of the eastern arm of Lake Van, and extensive damage was reported in the city of Van, the city of Ercis, and many smaller towns nearby. The region is near the middle of the elevated Turkish-Iranian Plateau in the collision zone between the Arabian and Eurasian Plates. Previous geodetic studies show ongoing N-S compressional strain in the area. We analyze coseismic InSAR from two Envisat ASAR descending-track pairs and one COSMO-SkyMed (CSK) descending-track pair, along with coseismic pixel offset tracking (sub-pixel correlation) along-track displacements from the CSK pair and coseismic 3-D displacements from continuous GPS station data posted to the Geohazards Supersite. We use SAR and GPS data to constrain a Bayesian inference method with Markov-chain Monte Carlo sampling to resolve the fault rupture location, size, and final slip distribution with posterior probability distribution estimates for the geometric parameters using a single planar fault model. The along-track (roughly N-S) displacements from the CSK data require that the main rupture dips to the north, and the geodetic inversion most probable strike and dip are 259+2/-1° and 43+3/-2°, respectively. These estimates are similar to moment tensor solutions and body waveform point-source solutions. A joint inversion of the geodetic data with the seismic waveforms (body and surface waves) was then performed with the finite fault geometry fixed to the values from the geodetic inversion to estimate the kinematic fault slip evolution during the earthquake. This combined analysis shows the fault rupture proceeded upward from the hypocenter near 18 km depth with little slip shallower than 8 km depth and most of the moment release in the first 10 s. All slip was completed in 14 s. We estimate that peak slip was between 5 and 15 m at a
NASA Astrophysics Data System (ADS)
Cubuk-Sabuncu, Yesim; Taymaz, Tuncay; Fichtner, Andreas
2016-04-01
We present a 3D radially anisotropic velocity model of the crust and uppermost mantle structure beneath the Sea of Marmara and surroundings based on the full waveform inversion method. The intense seismic activity and crustal deformation are observed in the Northwest Turkey due to transition tectonics between the strike-slip North Anatolian Fault (NAF) and the extensional Aegean region. We have selected and simulated complete waveforms of 62 earthquakes (Mw > 4.0) occurred during 2007-2015, and recorded at (Δ < 10°) distances. Three component earthquake data is obtained from broadband seismic stations of Kandilli Observatory and Earthquake Research Center (KOERI, Turkey), Hellenic Unified Seismic Network (HUSN, Greece) and Earthquake Research Center of Turkey (AFAD-DAD). The spectral-element solver of the wave equation, SES3D algorithm, is used to simulate seismic wave propagation in 3D spherical coordinates (Fichtner, 2009). The Large Scale Seismic Inversion Framework (LASIF) workflow tool is also used to perform full seismic waveform inversion (Krischer et al., 2015). The initial 3D Earth model is implemented from the multi-scale seismic tomography study of Fichtner et al. (2013). Discrepancies between the observed and simulated synthetic waveforms are determined using the time-frequency misfits which allows a separation between phase and amplitude information (Fichtner et al., 2008). The conjugate gradient optimization method is used to iteratively update the initial Earth model when minimizing the misfit. The inversion is terminated after 19 iterations since no further advances are observed in updated models. Our analysis revealed shear wave velocity variations of the shallow and deeper crustal structure beneath western Turkey down to depths of ~35-40 km. Low shear wave velocity anomalies are observed in the upper and mid crustal depths beneath major fault zones located in the study region. Low velocity zones also tend to mark the outline of young volcanic
Regional recreation demand and benefits model
Sutherland, R.J.
1983-03-01
This report describes a regional recreation demand and benefits model that is used to estimate recreation demand and value (consumers' surplus) of four activities at each of 195 sites in Washington, Oregon, Idaho, and western Montana. The recreation activities considered are camping, fishing, swimming, and boating. The model is a generalization of the single-site travel-cost method of estimating a recreation demand curve to virtually an unlimited number of sites. The major components of the analysis include the theory of recreation benefits, a travel-cost recreation demand curve, and a gravity model of regional recreation travel flows. Existing recreation benefits are estimated for each site in the region and for each activity. Recreation benefits of improved water quality in degraded rivers and streams in the Pacific Northwest are estimated on a county basis for Washington, Oregon, and Idaho. Although water quality is emphasized, the model has the capability of estimating demand and value for new or improved recreation sites at lakes, streams, or reservoirs.
Verifying Slab-Induced Waveform Effects beneath Central Taiwan by Three-dimensional Simulations
NASA Astrophysics Data System (ADS)
Huang, Yu-Ting; Zaho, Li; Chen, Po-fei; Chiao, Ling-Yun
2013-04-01
The Taiwan Island is a result of the convergence between the Eurasia and Philippine Sea plates. To what extent the east-dipping Eurasian slab extends northward beneath central Taiwan and the geometry of the slab east of Taiwan are important issues for understanding the geodynamics of the regional tectonics. However, structures in the upper mantle beneath Taiwan are poorly constrained in regional as well as global tomography models. The TAiwan Integrated GEodynamic Research (TAIGER) project deployed several well designed temporary arrays, and the broadband teleseismic data from stations along a north-south transect across Taiwan has been utilized to examine patterns of the first P waveform variations. The P waveforms observed in central Taiwan are generally characterized by earlier arrival times, reduced amplitudes, and broadened pulse widths relative to those observed in northern Taiwan, indicating the existence of a deep slab beneath central Taiwan. In this study, to verify those observations, we invoke the spectral-element method (SEM) to calculate the synthetic seismogram for the same dataset. Results for the 1D velocity model show that in central Taiwan the observed P waveforms have earlier arrival times, reduced amplitudes, and broadened pulse widths relative to the P waves in 1D model. We then invoke a hybrid model in which we use a regional 3D model as the background and introduce two slabs - an east-dipping slab south of Taiwan and a north-northwest-dipping slab offshore northeast Taiwan - with a suite of different slab configurations to determine the best velocity model that fits the previous observations.
Regional Seismic Identification Research:Processing, Transportability and Source Models
Walter, W; Mayeda, K; Rodgers, A; Taylor, S; Dodge, D; Matzel, E; Ganzberger, M
2004-07-09
Our identification research for the past several years has focused on the problem of correctly discriminating small-magnitude explosions from a background of earthquakes, mining tremors, and other events. Small magnitudes lead to an emphasis on regional waveforms. It has been shown that at each test site where earthquake and explosions are in close proximity and recorded at the same station, clear differences in the regional body waves such as the relative high frequency amplitudes of P and S waves can be used to discriminate between event types. However path and source effects can also induce such differences, therefore these must be quantified and accounted for. We have been using a specific technique called Magnitude and Distance Amplitude Correction (MDAC), with some success to account for some of these effects.
Full-waveform inversion in the time domain with an energy-weighted gradient
Zhang, Zhigang; Huang, Lianjie; Lin, Youzuo
2011-01-01
When applying full-waveform inversion to surface seismic reflection data, one difficulty is that the deep region of the model is usually not reconstructed as well as the shallow region. We develop an energy-weighted gradient method for the time-domain full-waveform inversion to accelerate the convergence rate and improve reconstruction of the entire model without increasing the computational cost. Three different methods can alleviate the problem of poor reconstruction in the deep region of the model: the layer stripping, depth-weighting and pseudo-Hessian schemes. The first two approaches need to subjectively choose stripping depths and weighting functions. The third one scales the gradient with only the forward propagation wavefields from sources. However, the Hessian depends on wavefields from both sources and receivers. Our new energy-weighted method makes use of the energies of both forward and backward propagated wavefields from sources and receivers as weights to compute the gradient. We compare the reconstruction of our new method with those of the conjugate gradient and pseudo-Hessian methods, and demonstrate that our new method significantly improves the reconstruction of both the shallow and deep regions of the model.
An MSK Waveform for Radar Applications
NASA Technical Reports Server (NTRS)
Quirk, Kevin J.; Srinivasan, Meera
2009-01-01
We introduce a minimum shift keying (MSK) waveform developed for use in radar applications. This waveform is characterized in terms of its spectrum, autocorrelation, and ambiguity function, and is compared with the conventionally used bi-phase coded (BPC) radar signal. It is shown that the MSK waveform has several advantages when compared with the BPC waveform, and is a better candidate for deep-space radar imaging systems such as NASA's Goldstone Solar System Radar.
Parameter Biases Introduced by Approximate Gravitational Waveforms
NASA Astrophysics Data System (ADS)
Farr, Benjamin; Coughlin, Scott; Le, John; Skeehan, Connor; Kalogera, Vicky
2013-04-01
The production of the most accurate gravitational waveforms from compact binary mergers require Einstein's equations to be solved numerically, a process far too expensive to produce the ˜10^7 waveforms necessary to estimate the parameters of a measured gravitational wave signal. Instead, parameter estimation depends on approximate or phenomenological waveforms to characterize measured signals. As part of the Ninja collaboration, we study the biases introduced by these methods when estimating the parameters of numerically produced waveforms.
Waveform retracking for improving inland water heights from altimetry
NASA Astrophysics Data System (ADS)
Uebbing, Bernd; Forootan, Ehsan; Kusche, Jürgen
2015-04-01
For more than two decades, satellite radar altimeters have been providing valuable information on level changes of seas and oceans. In recent years, the usage of satellite altimetry to monitor the water level changes of lakes and rivers, as well as in hydrology applications, has become a topic of rising interest. The altimeter emits a radar pulse, which is reflected at the nadir-surface and measures the two-way travel time, as well as the returned energy as a function of time, resulting in a return waveform. Over the open ocean the waveform shape corresponds to a theoretical model which can be used to infer information on range corrections, significant wave height or wind speed. However, the waveforms over lakes and rivers show patterns which are significantly influenced by signals reflected from land present in the altimeter footprint. This results in a variety of different waveforms shapes ranging from waveforms similar to the theoretical ocean case to completely different ones such as those including only small leading edges and large peaks on the trailing edge. These peaks considerably influence the estimation of the parameters of interest, such as the time origin, connected to the range information, particularly if they are located very close to the leading edge. To mitigate this problem, we present a retracking approach, which combines the advantages of sub-waveform retracking with a flexible waveform model, that allows to model symmetric and asymmetric Gaussian peaks. Based on a preliminary waveform analysis step, a defined window is applied to the total waveform and the parameters are estimated by a flexible fitting procedure. We retracked Topex/Poseidon, Jason-1 and Jason-2 data over several lakes, including the African lakes Volta and Victoria. The inferred lake level heights are evaluated by comparisons to water heights from in situ gauge observations, the Global Reservoir and Lake Monitoring database, as well as those derived from applying conventional
Generating nonlinear FM chirp waveforms for radar.
Doerry, Armin Walter
2006-09-01
Nonlinear FM waveforms offer a radar matched filter output with inherently low range sidelobes. This yields a 1-2 dB advantage in Signal-to-Noise Ratio over the output of a Linear FM waveform with equivalent sidelobe filtering. This report presents design and implementation techniques for Nonlinear FM waveforms.
Improving Regional Groundwater Models with Transmissivity Observations
NASA Astrophysics Data System (ADS)
Halford, K. J.
2013-12-01
Hydraulic-conductivity estimates in groundwater-flow models typically are constrained by a range for each hydrogeologic unit. These often-times wide ranges are derived from interpretations of many aquifer tests binned by hydrogeologic unit. Uncertainty is added to these ranges where hydraulic-conductivity estimates derived from aquifer tests use contributing thicknesses that differ from simulated thicknesses in a numerical model. Transmissivity observations from individual aquifer tests constrain model calibration better than hydraulic-conductivity ranges assigned to hydrogeologic units because simulated transmissivity and aquifer-test results are compared directly. Transmissivity comparisons require that simulated thicknesses and hydraulic conductivities for the volume investigated by the aquifer test be extracted from a model and integrated into a simulated transmissivity. Transmissivity observations have been ignored primarily because sampling simulated transmissivities is mechanically painful from complex models. A suite of programs called T-COMP has been developed to sample simulated transmissivities easily from regional MODFLOW models. Transmissivities of model cells are sampled where drawdown exceeds a user-defined threshold. Sampled transmissivities of model cells are averaged within a layer and summed between layers. This computationally intensive process occurs in separate programs that are executed prior to model calibration. Simulated transmissivities can be sampled quickly during calibration because nodes and their fractional contributions have been defined.
Regional CMS Modeling: Southwest Florida Gulf Coast
2016-05-01
Island , the City of Sarasota SPP at Lido Key, Sarasota County SPP at Venice Beach, and a number of federally authorized channels. Local projects exist...approximately 24.9 miles from the throat of Big Sarasota Pass and extends approximately 53.4 miles in the alongshore from Treasure Island to South Venice Inlet...regional CMS modeling framework that has been used to determine the morphologic change in multiple barrier -inlet systems along the Gulf Coast of
A methodology for modeling regional terrorism risk.
Chatterjee, Samrat; Abkowitz, Mark D
2011-07-01
Over the past decade, terrorism risk has become a prominent consideration in protecting the well-being of individuals and organizations. More recently, there has been interest in not only quantifying terrorism risk, but also placing it in the context of an all-hazards environment in which consideration is given to accidents and natural hazards, as well as intentional acts. This article discusses the development of a regional terrorism risk assessment model designed for this purpose. The approach taken is to model terrorism risk as a dependent variable, expressed in expected annual monetary terms, as a function of attributes of population concentration and critical infrastructure. This allows for an assessment of regional terrorism risk in and of itself, as well as in relation to man-made accident and natural hazard risks, so that mitigation resources can be allocated in an effective manner. The adopted methodology incorporates elements of two terrorism risk modeling approaches (event-based models and risk indicators), producing results that can be utilized at various jurisdictional levels. The validity, strengths, and limitations of the model are discussed in the context of a case study application within the United States.
The AEM and regional carbonate aquifer modeling.
Johnson, Cady; Mifflin, Martin
2006-01-01
The analytic element method (AEM) has been applied to a 15,000-km2 area of the Paleozoic carbonate rock terrain of Nevada. The focus is the Muddy River springs area, which receives 1.44 m3/s (51 ft3/s) of regionally derived ground water, and forms the Muddy River. The study was undertaken early in 2000 to support the development of a cooling water supply for a gas-fired generation facility 20 km south of the Muddy River springs. The primary objectives of the AEM modeling were to establish a better understanding of regional fluxes and boundary conditions and to provide a framework for examination of more local transient effects using MODFLOW. Geochemical evidence available in 2000 suggested two separate flow fields, one in the north discharging at the springs, and a southern area of small hydraulic gradients. To be conservative, however, hydraulic continuity between the two areas was maintained in the 2000 AEM model. Using new monitoring well data collected in the south, and analyses confirming that seasonal pumping effects in the north are not propagated to the south, a later AEM model that included a barrier calibrated with relative ease. The analytic element model was well suited for simulating an area larger than the immediate area of interest, was easy to modify as more information became available, and facilitated the stepwise development of multiple conceptual models of the site.
Semiempirical models of chromospheric flare regions
NASA Technical Reports Server (NTRS)
Machado, M. E.; Avrett, E. H.; Vernazza, J. E.; Noyes, R. W.
1980-01-01
Homogeneous plane-parallel semiempirical flare model atmospheres which reproduce observations in lines and continua of H I, Si I, C I, Ca II, and Mg II have a thin transition zone at the top of the enhanced chromosphere, indicating a significant amount of heating from the zone to the temperature minimum level. The minimum temperature is located deeper and is higher than in the quiet-sun and active-region models. The results do not agree with the particle-heated theoretical models, and it is suggested that the models of Brown (1973) and Henoux and Nakagawa (1977, 1978) do not include an essential term for heat conduction in their energy balance equations. It is concluded that substantial Ly-alpha radiative heating occurs in the upper chromosphere resulting from the conductive energy flux in the transition zone where the Ly-alpha line cools the gas.
Semiempirical models of chromospheric flare regions
NASA Technical Reports Server (NTRS)
Machado, M. E.; Avrett, E. H.; Vernazza, J. E.; Noyes, R. W.
1980-01-01
Homogeneous plane-parallel semiempirical flare model atmospheres which reproduce observations in lines and continua of H I, Si I, C I, Ca II, and Mg II have a thin transition zone at the top of the enhanced chromosphere, indicating a significant amount of heating from the zone to the temperature minimum level. The minimum temperature is located deeper and is higher than in the quiet-sun and active-region models. The results do not agree with the particle-heated theoretical models, and it is suggested that the models of Brown (1973) and Henoux and Nakagawa (1977, 1978) do not include an essential term for heat conduction in their energy balance equations. It is concluded that substantial Ly-alpha radiative heating occurs in the upper chromosphere resulting from the conductive energy flux in the transition zone where the Ly-alpha line cools the gas.
The waveform correlation event detection system global prototype software design
Beiriger, J.I.; Moore, S.G.; Trujillo, J.R.; Young, C.J.
1997-12-01
The WCEDS prototype software system was developed to investigate the usefulness of waveform correlation methods for CTBT monitoring. The WCEDS prototype performs global seismic event detection and has been used in numerous experiments. This report documents the software system design, presenting an overview of the system operation, describing the system functions, tracing the information flow through the system, discussing the software structures, and describing the subsystem services and interactions. The effectiveness of the software design in meeting project objectives is considered, as well as opportunities for code refuse and lessons learned from the development process. The report concludes with recommendations for modifications and additions envisioned for regional waveform-correlation-based detector.
Breast ultrasound computed tomography using waveform inversion with source encoding
NASA Astrophysics Data System (ADS)
Wang, Kun; Matthews, Thomas; Anis, Fatima; Li, Cuiping; Duric, Neb; Anastasio, Mark A.
2015-03-01
Ultrasound computed tomography (USCT) holds great promise for improving the detection and management of breast cancer. Because they are based on the acoustic wave equation, waveform inversion-based reconstruction methods can produce images that possess improved spatial resolution properties over those produced by ray-based methods. However, waveform inversion methods are computationally demanding and have not been applied widely in USCT breast imaging. In this work, source encoding concepts are employed to develop an accelerated USCT reconstruction method that circumvents the large computational burden of conventional waveform inversion methods. This method, referred to as the waveform inversion with source encoding (WISE) method, encodes the measurement data using a random encoding vector and determines an estimate of the speed-of-sound distribution by solving a stochastic optimization problem by use of a stochastic gradient descent algorithm. Computer-simulation studies are conducted to demonstrate the use of the WISE method. Using a single graphics processing unit card, each iteration can be completed within 25 seconds for a 128 × 128 mm2 reconstruction region. The results suggest that the WISE method maintains the high spatial resolution of waveform inversion methods while significantly reducing the computational burden.
Ultrasound waveform tomography using wave-energy-based preconditioning
NASA Astrophysics Data System (ADS)
Zhang, Zhigang; Huang, Lianjie
2013-03-01
Ultrasound waveform tomography using the conjugate gradient method produces images with different qualities in different regions of the imaging domain, partly because the ultrasound wave energy is dominant around transducer elements. In addition, this uneven distribution of the wave energy slows down the convergence of the inversion. Using the Hessian matrix to scale the gradients in waveform inversion can reduce the artifacts caused by the geometrical spreading and the defocusing effect resulting from the incomplete data coverage. However, it is computationally expensive to calculate the Hessian matrix. We develop a new ultrasound waveform tomography method that weights the gradient with the ultrasound wave energies of the forward and backward propagation wavefields. Our new method balances the wave energy distribution throughout the entire imaging domain. This method scales the gradients using the square root of the wave energy of forward propagated wavefields from sources and that of backpropagated synthetic wavefields from receivers. We numerically demonstrate that this new ultrasound waveform tomography method improves sound-speed reconstructions of breast tumors and accelerates the convergence of ultrasound waveform tomography.
Fusion of radionuclide and waveform information at CTBTO in support of the NPE12
NASA Astrophysics Data System (ADS)
Krysta, Monika; Kusmierczyk-Michulec, Jolanta; Kushida, Noriyuki
2013-04-01
Different technologies constitute the pillars of the system which monitors compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Each of the four technologies exploited by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has a monitoring network of its own which together constitute the International Monitoring System (IMS). CTBTO and its State Signatories make an effort to achieve synergy between the complementary information provided by the distinct networks in a process called data fusion. Seismic, infrasound and hydroacoustic monitoring technologies are based on detections of mechanical waves and referred to as waveforms. In an analysis process performed at the International Data Centre (IDC) those detections are subsequently associated to build events from which the mechanical waves originated. The association is more challenging in case of airborne radionuclide monitoring technology. A support in form of the computational results of atmospheric transport modelling is necessary in this case. But even with such a support, due to turbulent processes in the atmosphere, the events emanating the detected radionuclides are not easily identified. In fact, atmospheric transport modelling indicates the regions where a source could have been located rather than point-like events. However, if this information is appropriately merged with the waveform events, it could support evidence of their nuclear character or lack thereof. National Data Centres of State Signatories, which are responsible for the CTBT monitoring and verification at the national level, design and conduct annual exercises in order to test performance of the monitoring system and analysis of its detections. Exercise scenario, mixing real and fictitious components, is designed to ensure as broad a national expert involvement as possible. At the same time it offers a framework for testing and advancing data fusion capacity. In this presentation we propose to address data fusion as
2169 Steel Waveform Experiments
NASA Astrophysics Data System (ADS)
Furnish, M.; Alexander, C.; Reinhart, W.; Brown, J.
2013-06-01
In support of efforts to develop multiscale models of materials, we performed eight gas gun impact experiments on 2169 steel (21% Cr, 6% Ni, 9% Mn). These experiments provided shock, reshock and release velocimetry data, with initial shock stresses ranging from 10 to 50 GPa (particle velocities from 0.25 to 1.05 km/s). Both windowed and free-surface measurements were used, with samples 1 to 5 mm thick. The study focused on dynamic strength determination via the release/reshock paths. Reshock tests with explosively welded impactors produced clean results. The free-surface samples, which were steps on a single piece of steel, showed lower wavespeeds for thin (1 mm) samples than for thicker (2 or 4 mm) samples. A configuration used for the last three shots allowed release information to be determined from these free surface samples as well. The sample strength appears to increase with stress from ~1 GPa to ~3 GPa over this range, consistent with other recent work but about 40% above the Steinberg model. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Versatile Dual-Channel Waveform Generator
NASA Technical Reports Server (NTRS)
Staples, Edward J.; Lie, Sen; Ching, Michael; Budinger, James M.
1994-01-01
Programmable waveform generator synthesizes two independent waveforms simultaneously at frequencies up to 250 MHz. Can be in phase or out of phase with each other. Use of commercial integrated circuits helps keep cost low. Operation governed by BASIC source code enabling any user equipped with suitable personal computer to specify waveforms. User can modify source code to satisfy special needs. Other applications include simulation of Doppler waveforms for radar, and of video signals for testing color displays and computer monitors. With eventual substitution of gallium arsenide integrated circuits for its present silicon integrated circuits, instrument able to generate waveforms with 14-bit precision and sample rates as high as 2 GHz.
Versatile Dual-Channel Waveform Generator
NASA Technical Reports Server (NTRS)
Staples, Edward J.; Lie, Sen; Ching, Michael; Budinger, James M.
1994-01-01
Programmable waveform generator synthesizes two independent waveforms simultaneously at frequencies up to 250 MHz. Can be in phase or out of phase with each other. Use of commercial integrated circuits helps keep cost low. Operation governed by BASIC source code enabling any user equipped with suitable personal computer to specify waveforms. User can modify source code to satisfy special needs. Other applications include simulation of Doppler waveforms for radar, and of video signals for testing color displays and computer monitors. With eventual substitution of gallium arsenide integrated circuits for its present silicon integrated circuits, instrument able to generate waveforms with 14-bit precision and sample rates as high as 2 GHz.
NASA Astrophysics Data System (ADS)
Wang, Yi; Chevrot, Sébastien; Komatitsch, Dimitri; Monteiller, Vadim; Durochat, Clément
2016-04-01
Thanks to the deployment of permanent and temporary broadband arrays, coverage and data quality have dramatically improved in the last decade, especially for regional-scale studies. In addition, owing to the progress of high-performance resources and numerical simulation techniques, waveform inversion approaches nowadays become a viable alternative to classical asymptotic ray based tomographic approaches. Exploiting full waveforms in seismic tomography requires an efficient and precise method to solve the elastic wave equation in 3D inhomogeneous media. Since resolution of waveform inversion is limited by the seismic wavelength as well as the wavefield sampling density, it is crucial to exploit short-period teleseismic waves recorded by dense regional arrays. However, modeling the propagation of short-period body waves in heterogeneous media is still very challenging, even on the largest modern supercomputers. For this reason, we have developed a hybrid method that couples a global wave propagation method in a 1D Earth to a 3D spectral-element method in a regional domain. This hybrid method restricts the costly 3D computations to inside the regional domain, which dramatically decreases the computational cost, allows us to compute teleseismic wavefields down to 1s period, thus accounting for the complexities that affect the propagation of seismic waves in the regional domain. We present the first application of this new waveform inversion approach to broadband data coming from two dense transects deployed during the PYROPE experiment across the Pyrenees mountains. We obtain the first high-resolution lithospheric section of compressional and shear velocities across an orogenic belt. The tomographic model provides clear evidence for the under-thrusting of the thinned Iberian crust beneath the European plate and for the important role of rift-inherited mantle structures during the formation of the Pyrenees.
Non-linear 3-D Born shear waveform tomography in Southeast Asia
NASA Astrophysics Data System (ADS)
Panning, Mark P.; Cao, Aimin; Kim, Ahyi; Romanowicz, Barbara A.
2012-07-01
Southeast (SE) Asia is a tectonically complex region surrounded by many active source regions, thus an ideal test bed for developments in seismic tomography. Much recent development in tomography has been based on 3-D sensitivity kernels based on the first-order Born approximation, but there are potential problems with this approach when applied to waveform data. In this study, we develop a radially anisotropic model of SE Asia using long-period multimode waveforms. We use a theoretical 'cascade' approach, starting with a large-scale Eurasian model developed using 2-D Non-linear Asymptotic Coupling Theory (NACT) sensitivity kernels, and then using a modified Born approximation (nBorn), shown to be more accurate at modelling waveforms, to invert a subset of the data for structure in a subregion (longitude 75°-150° and latitude 0°-45°). In this subregion, the model is parametrized at a spherical spline level 6 (˜200 km). The data set is also inverted using NACT and purely linear 3-D Born kernels. All three final models fit the data well, with just under 80 per cent variance reduction as calculated using the corresponding theory, but the nBorn model shows more detailed structure than the NACT model throughout and has much better resolution at depths greater than 250 km. Based on variance analysis, the purely linear Born kernels do not provide as good a fit to the data due to deviations from linearity for the waveform data set used in this modelling. The nBorn isotropic model shows a stronger fast velocity anomaly beneath the Tibetan Plateau in the depth range of 150-250 km, which disappears at greater depth, consistent with other studies. It also indicates moderate thinning of the high-velocity plate in the middle of Tibet, consistent with a model where Tibet is underplated by Indian lithosphere from the south and Eurasian lithosphere from the north, in contrast to a model with continuous underplating by Indian lithosphere across the entire plateau. The n
NASA Astrophysics Data System (ADS)
Göttl, Franziska; Dettmering, Denise; Lucian Müller, Felix; Schwatke, Christian
2017-04-01
The estimation of lake water level variations with satellite altimetry is a challenging task because the majority of altimeter waveforms of smaller lakes are contaminated by land. In this study we used CryoSat-2 SAR data to estimate reliable water level time series for the four lakes: Tonle Sap (Cambodia), Vättern (Sweden), Okeechobee (Florida, USA) and Lough Neagh (North Ireland) with different size, surrounding landscape and water oscillation. Therefor a novel processing strategy was developed based on waveform classification, sub-waveform retracking and outlier rejection. The classification of waveforms is essential to find out which observations are performed over water and at the land-water transition. For this purpose, in a training area CryoSat-2 SAR waveforms were grouped into clusters with respect to the similarity of the amplitude, width and center of gravity of the waveforms by using the k-means algorithm. Especially for waveforms at the land-water transition the identification of the "best" sub-waveform becomes very important. The results are validated with modeled water heights derived from CryoSat-2 SAR data, multi-mission water level time series from classical altimetry and in-situ gauging data. The CryoSat-2 time series show similar quality although in our approach no model assumptions are applied. Especially for smaller lakes water heights can be derived from CryoSat-2 SAR data with higher precision than from classical altimeter data.
Action Potential Waveform Variability Limits Multi-Unit Separation in Freely Behaving Rats
Stratton, Peter; Cheung, Allen; Wiles, Janet; Kiyatkin, Eugene; Sah, Pankaj; Windels, François
2012-01-01
Extracellular multi-unit recording is a widely used technique to study spontaneous and evoked neuronal activity in awake behaving animals. These recordings are done using either single-wire or mulitwire electrodes such as tetrodes. In this study we have tested the ability of single-wire electrodes to discriminate activity from multiple neurons under conditions of varying noise and neuronal cell density. Using extracellular single-unit recording, coupled with iontophoresis to drive cell activity across a wide dynamic range, we studied spike waveform variability, and explored systematic differences in single-unit spike waveform within and between brain regions as well as the influence of signal-to-noise ratio (SNR) on the similarity of spike waveforms. We also modelled spike misclassification for a range of cell densities based on neuronal recordings obtained at different SNRs. Modelling predictions were confirmed by classifying spike waveforms from multiple cells with various SNRs using a leading commercial spike-sorting system. Our results show that for single-wire recordings, multiple units can only be reliably distinguished under conditions of high recording SNR (≥4) and low neuronal density (≈20,000/ mm3). Physiological and behavioural changes, as well as technical limitations typical of awake animal preparations, reduce the accuracy of single-channel spike classification, resulting in serious classification errors. For SNR <4, the probability of misclassifying spikes approaches 100% in many cases. Our results suggest that in studies where the SNR is low or neuronal density is high, separation of distinct units needs to be evaluated with great caution. PMID:22719894
2169 steel waveform experiments.
Furnish, Michael David; Alexander, C. Scott; Reinhart, William Dodd; Brown, Justin L.
2012-11-01
In support of LLNL efforts to develop multiscale models of a variety of materials, we have performed a set of eight gas gun impact experiments on 2169 steel (21% Cr, 6% Ni, 9% Mn, balance predominantly Fe). These experiments provided carefully controlled shock, reshock and release velocimetry data, with initial shock stresses ranging from 10 to 50 GPa (particle velocities from 0.25 to 1.05 km/s). Both windowed and free-surface measurements were included in this experiment set to increase the utility of the data set, as were samples ranging in thickness from 1 to 5 mm. Target physical phenomena included the elastic/plastic transition (Hugoniot elastic limit), the Hugoniot, any phase transition phenomena, and the release path (windowed and free-surface). The Hugoniot was found to be nearly linear, with no indications of the Fe phase transition. Releases were non-hysteretic, and relatively consistent between 3- and 5-mmthick samples (the 3 mm samples giving slightly lower wavespeeds on release). Reshock tests with explosively welded impactors produced clean results; those with glue bonds showed transient releases prior to the arrival of the reshock, reducing their usefulness for deriving strength information. The free-surface samples, which were steps on a single piece of steel, showed lower wavespeeds for thin (1 mm) samples than for thicker (2 or 4 mm) samples. A configuration used for the last three shots allows release information to be determined from these free surface samples. The sample strength appears to increase with stress from ~1 GPa to ~ 3 GPa over this range, consistent with other recent work but about 40% above the Steinberg model.
Models of transition regions in hybrid stars
NASA Technical Reports Server (NTRS)
Brosius, J. W.; Mullan, D. J.
1986-01-01
Models for the transition regions of six hybrid stars, four bright giants and two supergiants, are calculated. The models include mass loss and prescribe Alfven waves as the source of mechanical energy. The momentum and energy deposition rates required at each level of the atmosphere are evaluated. The final models for all six stars have mass loss rates lying below the current VLA upper limits by factors of two to ten, and have densities which agree with those derived by density-sensitive line ratios. The density vs. temperature structure in Alpha TrA agree well with that derived by Hartmann et al. (1985). Wave amplitudes and magnetic field strengths are derived as functions of height, and the amplitudes are found to agree well with the observed line widths in Alpha TrA.
Analysing the ventricular fibrillation waveform.
Reed, Matthew J; Clegg, Gareth R; Robertson, Colin E
2003-04-01
The surface electrocardiogram associated with ventricular fibrillation has been of interest to researchers for some time. Over the last few decades, techniques have been developed to analyse this signal in an attempt to obtain more information about the state of the myocardium and the chances of successful defibrillation. This review looks at the implications of analysing the VF waveform and discusses the various techniques that have been used, including fast Fourier transform analysis, wavelet transform analysis and mathematical techniques such as chaos theory.
Determinism in synthesized chaotic waveforms.
Corron, Ned J; Blakely, Jonathan N; Hayes, Scott T; Pethel, Shawn D
2008-03-01
The output of a linear filter driven by a randomly polarized square wave, when viewed backward in time, is shown to exhibit determinism at all times when embedded in a three-dimensional state space. Combined with previous results establishing exponential divergence equivalent to a positive Lyapunov exponent, this result rigorously shows that such reverse-time synthesized waveforms appear equally to have been produced by a deterministic chaotic system.
Why Waveform Correlation Sometimes Fails
NASA Astrophysics Data System (ADS)
Carmichael, J.
2015-12-01
Waveform correlation detectors used in explosion monitoring scan noisy geophysical data to test two competing hypotheses: either (1) an amplitude-scaled version of a template waveform is present, or, (2) no signal is present at all. In reality, geophysical wavefields that are monitored for explosion signatures include waveforms produced by non-target sources that are partially correlated with the waveform template. Such signals can falsely trigger correlation detectors, particularly at low thresholds required to monitor for smaller target explosions. This challenge is particularly formidable when monitoring known test sites for seismic disturbances, since uncatalogued natural seismicity is (generally) more prevalent at lower magnitudes, and could be mistaken for small explosions. To address these challenges, we identify real examples in which correlation detectors targeting explosions falsely trigger on both site-proximal earthquakes (Figure 1, below) and microseismic "noise". Motivated by these examples, we quantify performance loss when applying these detectors, and re-evaluate the correlation-detector's hypothesis test. We thereby derive new detectors from more general hypotheses that admit unknown background seismicity, and apply these to real data. From our treatment, we derive "rules of thumb'' for proper template and threshold selection in heavily cluttered signal environments. Last, we answer the question "what is the probability of falsely detecting an earthquake collocated at a test site?", using correlation detectors that include explosion-triggered templates. Figure Top: An eight-channel data stream (black) recorded from an earthquake near a mine. Red markers indicate a detection. Middle: The correlation statistic computed by scanning the template against the data stream at top. The red line indicates the threshold for event declaration, determined by a false-alarm on noise probability constraint, as computed from the signal-absent distribution using
An Objective Waveform Comparison Technique
1983-10-01
time histories is what is important in designing a structure to sustain such waveforms. Note that the definition of E (t) in Equation 2.10...4550 DEM(I) = (EN(I)-EN(I-1))*DXI 4560 DEMAX a MAX(DE(I)fDEMAX) 4570 DENIM = MIN(DE(X)pDEMIN) 4580 DEPMAX = MAX(DEP(I)tDEPMAX) 4590 DEMMIN = MIN(DEM(I
Photonic Arbitrary Waveform Generation Technology
2006-06-01
filters or ring resonator based technologies [26-29]. Key aspects of the filter technology are the flatness of the filter channel, the crosstalk...photodetectors would also be warranted. 28 References [1] K. Nosu, “ Advanced coherent lightwave technologies ,” IEEE Commun. Magn,, vol. 26...AFRL-SN-RS-TR-2006-208 Final Technical Report June 2006 PHOTONIC ARBITRARY WAVEFORM GENERATION TECHNOLOGY University of
Modeling Regional Economic Impacts of Natural Disasters
NASA Astrophysics Data System (ADS)
Boissonnade, A.; Hallegate, S.; Muir-Wood, R.; Schlumberger, M.; Onur, T.
2007-05-01
Common features of natural disasters are intense regional impacts and the need for assessing their economic impacts on the construction sectors. The years 2004 and 2005 were record-setting time for natural disasters with major disasters or catastrophic (Cat) events all around the world with dramatic consequences in human lives and economic losses around the world, affecting developed and developing countries. Although there is a large body of literature on assessing the impact of cat events, there is little available research on the quantification and modeling of the regional economic impact of such events on the cost and length of reconstruction. Current available econometric models have serious limitations because they need detailed information for modeling the complex interactions between the different stakeholders of the economy at a regional level that is generally not available. Also, very little research was performed for quantifying the demand surge, defined as the sudden increase in the cost of repairs due to amplified payments, following a hurricane or a series of hurricane events or other natural disasters. Demand surge is an important component of the overall economic impact of cat events and there is a need to better quantify it. This paper presents results of a research program that started after the 2004 and 2005 U.S. hurricane seasons. A large data set of economic and observed losses resulting from the hurricanes that affected Florida and the Gulf states in the US was collected at county level. This provided us with the basis for assessing the change in repair costs before and after these historical events, to quantify the demand surge (after removing the underlying baseline trends) at several dozens of locations across the areas affected, and to provide information on how the changes in demand surge vary spatially and temporally in affected areas for which the amount of structure losses were reported. A parallel research effort was undertaken for
Savage, B; Peter, D; Covellone, B; Rodgers, A; Tromp, J
2009-07-02
Efforts to update current wave speed models of the Middle East require a thoroughly tested database of sources and recordings. Recordings of seismic waves traversing the region from Tibet to the Red Sea will be the principal metric in guiding improvements to the current wave speed model. Precise characterizations of the earthquakes, specifically depths and faulting mechanisms, are essential to avoid mapping source errors into the refined wave speed model. Errors associated with the source are manifested in amplitude and phase changes. Source depths and paths near nodal planes are particularly error prone as small changes may severely affect the resulting wavefield. Once sources are quantified, regions requiring refinement will be highlighted using adjoint tomography methods based on spectral element simulations [Komatitsch and Tromp (1999)]. An initial database of 250 regional Middle Eastern events from 1990-2007, was inverted for depth and focal mechanism using teleseismic arrivals [Kikuchi and Kanamori (1982)] and regional surface and body waves [Zhao and Helmberger (1994)]. From this initial database, we reinterpreted a large, well recorded subset of 201 events through a direct comparison between data and synthetics based upon a centroid moment tensor inversion [Liu et al. (2004)]. Evaluation was done using both a 1D reference model [Dziewonski and Anderson (1981)] at periods greater than 80 seconds and a 3D model [Kustowski et al. (2008)] at periods of 25 seconds and longer. The final source reinterpretations will be within the 3D model, as this is the initial starting point for the adjoint tomography. Transitioning from a 1D to 3D wave speed model shows dramatic improvements when comparisons are done at shorter periods, (25 s). Synthetics from the 1D model were created through mode summations while those from the 3D simulations were created using the spectral element method. To further assess errors in source depth and focal mechanism, comparisons between the
Automated Analysis, Classification, and Display of Waveforms
NASA Technical Reports Server (NTRS)
Kwan, Chiman; Xu, Roger; Mayhew, David; Zhang, Frank; Zide, Alan; Bonggren, Jeff
2004-01-01
A computer program partly automates the analysis, classification, and display of waveforms represented by digital samples. In the original application for which the program was developed, the raw waveform data to be analyzed by the program are acquired from space-shuttle auxiliary power units (APUs) at a sampling rate of 100 Hz. The program could also be modified for application to other waveforms -- for example, electrocardiograms. The program begins by performing principal-component analysis (PCA) of 50 normal-mode APU waveforms. Each waveform is segmented. A covariance matrix is formed by use of the segmented waveforms. Three eigenvectors corresponding to three principal components are calculated. To generate features, each waveform is then projected onto the eigenvectors. These features are displayed on a three-dimensional diagram, facilitating the visualization of the trend of APU operations.
NASA Astrophysics Data System (ADS)
Pekowsky, Larne
2012-03-01
Two important advances have occurred in recent years which have brought us closer to the goal of observing and interpreting gravitational waves from coalescing compact objects: the successful construction and operation of a world-wide network of ground-based gravitational-wave detectors and the impressive success of numerical relativity in successfully simulating the merger phase of Binary Black Hole (BBH) coalescence. The aim of the NINJA project is to study the sensitivity of gravitational-wave analysis pipelines to numerical simulations of waveforms and foster close collaboration between numerical relativists and data analysts. NINJA-1 was a huge success, over 75 numerical relativists and data analysis participated in the contribution of a simulated data set containing numerical waveforms, analysis of this data and interpreting the results of this analysis. The follow-up project, NINJA-2 is currently underway. We present some of the goals of NINJA-2 and discuss aspects of the construction of the catalog of waveforms which will be used.
Energy-efficient waveform shapes for neural stimulation revealed with genetic algorithm
Wongsarnpigoon, Amorn; Grill, Warren M.
2010-01-01
The energy efficiency of stimulation is an important consideration for battery-powered implantable stimulators. We used a genetic algorithm (GA) to determine the energy-optimal waveform shape for neural stimulation. The GA was coupled to a computational model of extracellular stimulation of a mammalian myelinated axon. As the GA progressed, waveforms became increasingly energy-efficient and converged upon an energy-optimal shape. The results of the GA were consistent across several trials, and resulting waveforms resembled truncated Gaussian curves. When constrained to monophasic cathodic waveforms, the GA produced waveforms that were symmetric about the peak, which occurred approximately during the middle of the pulse. However, when the cathodic waveforms were coupled to rectangular charge-balancing anodic pulses, the location and sharpness of the peak varied with the duration and timing (i.e., before or after cathodic phase) of the anodic phase. In a model of a population of mammalian axons and in vivo experiments on cat sciatic nerve, the GA-optimized waveforms were more energy-efficient and charge-efficient than several conventional waveform shapes used in neural stimulation. If used in implantable neural stimulators, GA-optimized waveforms could prolong battery life, thereby reducing the frequency of recharge intervals, the volume of implanted pulse generators, and the costs and risks of battery-replacement surgeries. PMID:20571186
Energy-efficient waveform shapes for neural stimulation revealed with a genetic algorithm
NASA Astrophysics Data System (ADS)
Wongsarnpigoon, Amorn; Grill, Warren M.
2010-08-01
The energy efficiency of stimulation is an important consideration for battery-powered implantable stimulators. We used a genetic algorithm (GA) to determine the energy-optimal waveform shape for neural stimulation. The GA was coupled to a computational model of extracellular stimulation of a mammalian myelinated axon. As the GA progressed, waveforms became increasingly energy efficient and converged upon an energy-optimal shape. The results of the GA were consistent across several trials, and resulting waveforms resembled truncated Gaussian curves. When constrained to monophasic cathodic waveforms, the GA produced waveforms that were symmetric about the peak, which occurred approximately during the middle of the pulse. However, when the cathodic waveforms were coupled to rectangular charge-balancing anodic pulses, the location and sharpness of the peak varied with the duration and timing (i.e., before or after the cathodic phase) of the anodic phase. In a model of a population of mammalian axons and in vivo experiments on a cat sciatic nerve, the GA-optimized waveforms were more energy efficient and charge efficient than several conventional waveform shapes used in neural stimulation. If used in implantable neural stimulators, GA-optimized waveforms could prolong battery life, thereby reducing the frequency of recharge intervals, the volume of implanted pulse generators, and the costs and risks of battery-replacement surgeries.
Modeling Local and Regional Wave Propagation
NASA Astrophysics Data System (ADS)
Apoloner, Maria-Theresia; Bokelmann, Götz
2013-04-01
Seismograms reflect the combined effects of the source, recording instrument, ambient noise, and the propagation path. Especially for recording at distances smaller then 10° the signal is affected mainly by the crustal structure, as waves propagate in the crust and/or along Moho. Therefore appearance of regional seismograms varies strongly, which complicates record interpretation and phase identification severely. However, for earthquakes with small magnitudes, close distance records are the only ones available with a sufficient signal at all. Due to sparse seismic station coverage and the use of only the most distinct phases, typically Pg and Sg, localization can not always be ensured. Yet, retrieving accurate earthquake location, including depth information and the relation with faults is important for understanding tectonic processes and for estimating seismic hazard. Prior works by e.g. Ma (2010) show the benefit of using additional regional phases for localization, in particular depth. At local and regional distances the challenge lies in robustly detecting and identifying these phases correctly, which are usually superimposed by the coda of the P- and S-phase and sometimes even arrive simultaneously. In this work we want to shed light on the different influences on seismograms at local distances < 200 km. Starting with a simple crust-mantle model we calculate seismic recordings for sources at varying distances and depths. In addition we look at the changes induced by source mechanisms at diverse azimuths surrounding the source. Particularly the change in amplitude, time and frequency induced by the varying parameters is investigated. According to the phases identified in the diverse synthetic record sections, an overview of propagation characteristics is given. Our goal is to understand the usable information content of regional phases. Based on this information the theoretical performance of methods for identification of additional regional phases can be
Regional geothermal 3D modelling in Denmark
NASA Astrophysics Data System (ADS)
Poulsen, S. E.; Balling, N.; Bording, T. S.; Nielsen, S. B.
2012-04-01
Weichselian glaciation is included in the model procedure. The ability of MODFLOW for simulating heat conduction is demonstrated in simple test cases. The regional geothermal model is then utilized for modelling the subsurface temperature distribution and contouring updated temperature maps for geothermal reservoirs in Denmark.
Using waveform information in nonlinear data assimilation.
Rey, Daniel; Eldridge, Michael; Morone, Uriel; Abarbanel, Henry D I; Parlitz, Ulrich; Schumann-Bischoff, Jan
2014-12-01
Information in measurements of a nonlinear dynamical system can be transferred to a quantitative model of the observed system to establish its fixed parameters and unobserved state variables. After this learning period is complete, one may predict the model response to new forces and, when successful, these predictions will match additional observations. This adjustment process encounters problems when the model is nonlinear and chaotic because dynamical instability impedes the transfer of information from the data to the model when the number of measurements at each observation time is insufficient. We discuss the use of information in the waveform of the data, realized through a time delayed collection of measurements, to provide additional stability and accuracy to this search procedure. Several examples are explored, including a few familiar nonlinear dynamical systems and small networks of Colpitts oscillators.
NASA Astrophysics Data System (ADS)
Ogungbemi, Kayode; Han, Xianming; Misra, Prabhakar
2010-02-01
The laser optogalvanic (OG) waveforms associated with the 1s5 -- 2pj (j=7,8,9) transitions of neon in a hollow discharge lamp have been investigated as a function of discharge current (2.0 -- 19.0 mA). We have refined a mathematical model in determining the amplitudes, decay constants, and time constants associated with these transitions. Monte Carlo least-squares fitting of these waveforms has helped to specifically determine the decay rate constant (ai), exponential rates (bi) and time constant (τ) parameters associated with the evolution of the OG signals. In our investigation of the 1s5 -- 2pj (j=7,8,9)optogalvanic transitions of neon, we have measured the intensity of each transition (3.65*10-28 , 1.43*10-27 and 5.82*10-27 cm-1/mole-cm-2, respectively), which in turn has provided insight into the excitation temperature of the plasma (estimated to be 2847±285 K). The population distribution of the excited neon atoms in the pertinent energy levels has also been estimated using the Heisenberg Uncertainty Principle. )
NASA Astrophysics Data System (ADS)
Yuan, Shihao; Fuji, Nobuaki; Singh, Satish; Borisov, Dmitry
2017-06-01
We present a methodology to invert seismic data for a localized area by combining source-side wavefield injection and receiver-side extrapolation method. Despite the high resolving power of seismic full waveform inversion, the computational cost for practical scale elastic or viscoelastic waveform inversion remains a heavy burden. This can be much more severe for time-lapse surveys, which require real-time seismic imaging on a daily or weekly basis. Besides, changes of the structure during time-lapse surveys are likely to occur in a small area rather than the whole region of seismic experiments, such as oil and gas reservoir or CO2 injection wells. We thus propose an approach that allows to image effectively and quantitatively the localized structure changes far deep from both source and receiver arrays. In our method, we perform both forward and back propagation only inside the target region. First, we look for the equivalent source expression enclosing the region of interest by using the wavefield injection method. Second, we extrapolate wavefield from physical receivers located near the Earth's surface or on the ocean bottom to an array of virtual receivers in the subsurface by using correlation-type representation theorem. In this study, we present various 2-D elastic numerical examples of the proposed method and quantitatively evaluate errors in obtained models, in comparison to those of conventional full-model inversions. The results show that the proposed localized waveform inversion is not only efficient and robust but also accurate even under the existence of errors in both initial models and observed data.
NASA Astrophysics Data System (ADS)
Kubo, Hisahiko; Suzuki, Wataru; Aoi, Shin; Sekiguchi, Haruko
2016-10-01
The detailed source rupture process of the M 7.3 event (April 16, 2016, 01:25, JST) of the 2016 Kumamoto, Japan, earthquakes was derived from strong-motion waveforms using multiple-time-window linear waveform inversion. Based on the observations of surface ruptures, the spatial distribution of aftershocks, and the geodetic data, a realistic curved fault model was developed for source-process analysis of this event. The seismic moment and maximum slip were estimated as 5.5 × 1019 Nm ( M w 7.1) and 3.8 m, respectively. The source model of the M 7.3 event had two significant ruptures. One rupture propagated toward the northeastern shallow region at 4 s after rupture initiation and continued with large slips to approximately 16 s. This rupture caused a large slip region 10-30 km northeast of the hypocenter that reached the caldera of Mt. Aso. Another rupture propagated toward the surface from the hypocenter at 2-6 s and then propagated toward the northeast along the near surface at 6-10 s. A comparison with the result of using a single fault plane model demonstrated that the use of the curved fault model led to improved waveform fit at the stations south of the fault. The source process of the M 6.5 event (April 14, 2016, 21:26, JST) was also estimated. In the source model obtained for the M 6.5 event, the seismic moment was 1.7 × 1018 Nm ( M w 6.1), and the rupture with large slips propagated from the hypocenter to the surface along the north-northeast direction at 1-6 s. The results in this study are consistent with observations of the surface ruptures. [Figure not available: see fulltext. Caption: .
Lin, Youzuo; Huang, Lianjie; Zhang, Zhigang
2011-01-01
Double-difference waveform inversion is a promising tool for quantitative monitoring for enhanced geothermal systems (EGS). The method uses time-lapse seismic data to jointly inverts for reservoir changes. Due to the ill-posedness of waveform inversion, it is a great challenge to obtain reservoir changes accurately and efficiently, particularly when using timelapse seismic reflection data. To improve reconstruction, we develop a spatially-variant total-variation regularization scheme into double-difference waveform inversion to improve the inversion accuracy and robustness. The new regularization scheme employs different regularization parameters in different regions of the model to obtain an optimal regularization in each area. We compare the results obtained using a spatially-variant parameter with those obtained using a constant regularization parameter. Utilizing a spatially-variant regularization scheme, the target monitoring regions are well reconstructed and the image noise is significantly reduced outside the monitoring regions. Our numerical examples demonstrate that the spatially-variant total-variation regularization scheme provides the flexibility to regularize local regions based on the a priori spatial information without increasing computational costs and the computer memory requirement.
Offset prediction for charge-balanced stimulus waveforms.
Woods, V M; Triantis, I F; Toumazou, C
2011-08-01
Functional electrical stimulation with cuff electrodes involves the controlled injection of current into an electrically excitable tissue for sensory or motor rehabilitation. Some charge injected during stimulation is 'lost' at the electrode-electrolyte interface when the charge carrier is translated from an electron to an ion in the solution. The process of charge injection through chemical reactions can reduce electrode longevity and implant biocompatibility. Conventionally, the excess charge is minimized by complex hardware solutions, which are often not appropriate for robust long-term implantable solutions. Here, we present a method of waveform design that minimizes irrecoverable charge during continuous pulsing through the use of biphasic waveforms with unequally charged phases. We developed an equivalent electrical model of the electrode-electrolyte impedance based on the electrode's surface chemistry during psuedo-bipolar stimulation conditions. Simulations with the equivalent circuit determined the uncompensated charge to be a function of stimulus parameters. In vitro stimulation experiments in saline confirmed that we could preemptively compensate for the excess charge following biphasic stimulus waveforms. As a result, there was a 92% reduction in the pre-pulse potential after a pulse train with this new waveform design when compared to stimulation with conventional biphasic waveforms.
Evaluation of novel stimulus waveforms for deep brain stimulation
Foutz, TJ; McIntyre, CC
2010-01-01
Deep brain stimulation (DBS) is an established therapy for the treatment of a wide range of neurological disorders. Historically, DBS and other neurostimulation technologies have relied on rectangular stimulation waveforms to impose their effects on the nervous system. Recent work has suggested that non-rectangular waveforms may have advantages over the traditional rectangular pulse. Therefore, we used detailed computer models to compare a range of charge-balanced biphasic waveforms with rectangular, exponential, triangular, Gaussian, and sinusoidal stimulus pulse shapes. We explored the neural activation energy of these waveforms in both intracellular and extracellular stimulation. In the context of extracellular stimulation, we compared their effects on both axonal fibers of passage and projection neurons. Finally, we evaluated the impact of delivering the waveforms through a clinical DBS electrode, as opposed to a theoretical point source. Our results suggest that DBS with a 1 ms centered-triangular pulse can decrease energy consumption by 64 % when compared to the standard 100 μs rectangular pulse (energy cost of 48 nJ and 133 nJ, respectively, to stimulate 50 % of a distributed population of axons) and can decrease energy consumption by 10 % when compared to the most energy efficient rectangular pulse (1.25 ms duration). In turn, there may be measureable energy savings when using appropriately designed non-rectangular pulses in clinical DBS applications, thereby warranting further experimental investigation. PMID:21084732
Evaluation of novel stimulus waveforms for deep brain stimulation
NASA Astrophysics Data System (ADS)
Foutz, Thomas J.; McIntyre, Cameron C.
2010-12-01
Deep brain stimulation (DBS) is an established therapy for the treatment of a wide range of neurological disorders. Historically, DBS and other neurostimulation technologies have relied on rectangular stimulation waveforms to impose their effects on the nervous system. Recent work has suggested that non-rectangular waveforms may have advantages over the traditional rectangular pulse. Therefore, we used detailed computer models to compare a range of charge-balanced biphasic waveforms with rectangular, exponential, triangular, Gaussian and sinusoidal stimulus pulse shapes. We explored the neural activation energy of these waveforms for both intracellular and extracellular current-controlled stimulation conditions. In the context of extracellular stimulation, we compared their effects on both axonal fibers of passage and projection neurons. Finally, we evaluated the impact of delivering the waveforms through a clinical DBS electrode, as opposed to a theoretical point source. Our results suggest that DBS with a 1 ms centered-triangular pulse can decrease energy consumption by 64% when compared with the standard 100 µs rectangular pulse (energy cost of 48 and 133 nJ, respectively, to stimulate 50% of a distributed population of axons) and can decrease energy consumption by 10% when compared with the most energy efficient rectangular pulse (1.25 ms duration). In turn, there may be measureable energy savings when using appropriately designed non-rectangular pulses in clinical DBS applications, thereby warranting further experimental investigation.