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Sample records for infrasound source observed

  1. Infrasound Observations from Lightning

    NASA Astrophysics Data System (ADS)

    Arechiga, R. O.; Johnson, J. B.; Edens, H. E.; Thomas, R. J.; Jones, K. R.

    2008-12-01

    To provide additional insight into the nature of lightning, we have investigated its infrasound manifestations. An array of three stations in a triangular configuration, with three sensors each, was deployed during the Summer of 2008 (July 24 to July 28) in the Magdalena mountains of New Mexico, to monitor infrasound (below 20 Hz) sources due to lightning. Hyperbolic formulations of time of arrival (TOA) measurements and interferometric techniques were used to locate lightning sources occurring over and outside the network. A comparative analysis of simultaneous Lightning Mapping Array (LMA) data and infrasound measurements operating in the same area was made. The LMA locates the sources of impulsive RF radiation produced by lightning flashes in three spatial dimensions and time, operating in the 60 - 66 MHz television band. The comparison showed strong evidence that lightning does produce infrasound. This work is a continuation of the study of the frequency spectrum of thunder conducted by Holmes et al., who reported measurements of infrasound frequencies. The integration of infrasound measurements with RF source localization by the LMA shows great potential for improved understanding of lightning processes.

  2. Analysis of Signals from an Unique Ground-Truth Infrasound Source Observed at IMS Station IS26 in Southern Germany

    NASA Astrophysics Data System (ADS)

    Koch, Karl

    2010-05-01

    Quantitative modeling of infrasound signals and development and verification of the corresponding atmospheric propagation models requires the use of well-calibrated sources. Numerous sources have been detected by the currently installed network of about 40 of the final 60 IMS infrasound stations. Besides non-nuclear explosions such as mining and quarry blasts and atmospheric phenomena like auroras, these sources include meteorites, volcanic eruptions and supersonic aircraft including re-entering spacecraft and rocket launches. All these sources of infrasound have one feature in common, in that their source parameters are not precisely known and the quantitative interpretation of the corresponding signals is therefore somewhat ambiguous. A source considered well-calibrated has been identified producing repeated infrasound signals at the IMS infrasound station IS26 in the Bavarian forest. The source results from propulsion tests of the ARIANE-5 rocket's main engine at a testing facility near Heilbronn, southern Germany. The test facility is at a range of 320 km and a backazimuth of ~280° from IS26. Ground-truth information was obtained for nearly 100 tests conducted in a 5-year period. Review of the available data for IS26 revealed that at least 28 of these tests show signals above the background noise level. These signals are verified based on the consistency of various signal parameters, e.g., arrival times, durations, and estimates of propagation characteristics (backazimuth, apparent velocity). Signal levels observed are a factor of 2-8 above the noise and reach values of up to 250 mPa for peak amplitudes, and a factor of 2-3 less for RMS measurements. Furthermore, only tests conducted during the months from October to April produce observable signals, indicating a significant change in infrasound propagation conditions between summer and winter months.

  3. Infrasound Observations from the Source Physics Experiment (Tests 1 and 2) at the Nevada National Security Site

    DTIC Science & Technology

    2012-09-01

    INFRASOUND OBSERVATIONS FROM THE SOURCE PHYSICS EXPERIMENT ( TESTS 1 AND 2) AT THE NEVADA NATIONAL SECURITY SITE Kyle R. Jones1, Rod W. Whitaker2...series of explosions, we have the unique and rare opportunity to study infrasound generated by a well-characterized source from the same borehole ...two explosive tests (SPE-N-1 and SPE-N-2) were successfully conducted on May 3 and October 25, 2011, respectively. SPE-N-1 had a yield of 0.1 tons at

  4. Ten Years of Infrasound Observation in Korea

    NASA Astrophysics Data System (ADS)

    Lee, Hee-Il; Che, Il-Young; Kim, Tae Sung

    2010-05-01

    Over the ten years after the installation of our first seismo-acoustic array station (CHNAR) in September 1999, Korea Institute of Geoscience and Mineral Resources (KIGAM) has been continuously observing infrasound with an infrasound array network, named KIN (Korean Infrasound Network) in Korea. This network consists of seven seismo-acoustic arrays (BRDAR, KMPAR, CHNAR, YAGAR, KSGAR, ULDAR and TJIAR). The aperture size of the smallest array (KMPAR and TJIAR) is about 300m and the largest is about 1.4km. The number of acoustic gauges are between 4 (TJIAR) and 18 (YAGAR), and 1 or 5 seismometers are collocated at the center of the acoustic array. All seismic and infrasonic signals of the arrays are digitized at 40 samples/sec and transmitted to KIGAM in real time. Many interesting infrasound signals associated with different kind of anthropogenic source as well as natural one are detected by KIN. Ten years of seismo-acoustic data are analyzed by using PMCC program, and identified more than five thousand of infrasonic events and catalogued in our infrasound database. This database is used to study characteristics of seasonally dependent propagation of the infrasound wave in local scale, as well as to better understand how atmospheric condition affects the detection ratio at a specific station throughout the year. It also played a valuable role in discriminating the anthropogenic events such as the second nuclear test on 25 May 2009 in North Korea, from natural earthquakes, which is important in estimating the seismicity in Korea.

  5. GT0 Explosion Sources for IMS Infrasound Calibration: Charge Design and Yield Estimation from Near-source Observations

    NASA Astrophysics Data System (ADS)

    Gitterman, Y.; Hofstetter, R.

    2014-03-01

    Three large-scale on-surface explosions were conducted by the Geophysical Institute of Israel (GII) at the Sayarim Military Range, Negev desert, Israel: about 82 tons of strong high explosives in August 2009, and two explosions of about 10 and 100 tons of ANFO explosives in January 2011. It was a collaborative effort between Israel, CTBTO, USA and several European countries, with the main goal to provide fully controlled ground truth (GT0) infrasound sources, monitored by extensive observations, for calibration of International Monitoring System (IMS) infrasound stations in Europe, Middle East and Asia. In all shots, the explosives were assembled like a pyramid/hemisphere on dry desert alluvium, with a complicated explosion design, different from the ideal homogenous hemisphere used in similar experiments in the past. Strong boosters and an upward charge detonation scheme were applied to provide more energy radiated to the atmosphere. Under these conditions the evaluation of the actual explosion yield, an important source parameter, is crucial for the GT0 calibration experiment. Audio-visual, air-shock and acoustic records were utilized for interpretation of observed unique blast effects, and for determination of blast wave parameters suited for yield estimation and the associated relationships. High-pressure gauges were deployed at 100-600 m to record air-blast properties, evaluate the efficiency of the charge design and energy generation, and provide a reliable estimation of the charge yield. The yield estimators, based on empirical scaled relations for well-known basic air-blast parameters—the peak pressure, impulse and positive phase duration, as well as on the crater dimensions and seismic magnitudes, were analyzed. A novel empirical scaled relationship for the little-known secondary shock delay was developed, consistent for broad ranges of ANFO charges and distances, which facilitates using this stable and reliable air-blast parameter as a new potential

  6. Seismo-acoustic analysis of the ocean swell sources observed with Romanian infrasound array and seismic stations

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela; Grecu, Bogdan; Popa, Mihaela

    2015-04-01

    Romanian Plostina infrasound array (IPLOR) is deployed in the central part of the country, in Vrancea region. Presently, IPLOR array configuration includes 6 elements equipped with Chaparral Physics sensors and with aperture of about 2.5 km. For the purpose of assessing the IPLOR performance in observing various types of infrasound sources, over five years of data (since June 2009 to present) were processed. Signal interactive analysis was performed using WinPMCC software. The detection results show that the station response was gradually improved, as the number of array elements increased from three to six, and wind noise reduction conditions were enhanced. A larger number of detected signals and a better array resolution at lower frequency were noticed as well. Microbaroms - the interaction of ocean swell with the atmosphere - represent a relevant type of infrasonic source present in the IPLOR detection plots, for which the signal characterization has been enhanced with the array upgrading process. IPLOR detection capability related to this energetic long-period infrasound waves, which propagate over large distances, shows an alternating behavior, being strongly influenced by the upper atmospheric winds, i.e. seasonally dependent stratospheric winds. The ocean swell can be considered as a seismo-acoustic source, leaving an imprint on both seismic and infrasonic recordings. The interaction with the atmosphere generates infrasound (microbarom), while the interaction with the sea floor emits seismic signal (microseism). Microbaroms have a sinusoidal wave character with a dominant period of 5 s. Due to low damping at this period in stratospheric wave duct, microbaroms are observed over large distance ranges up to a few thousand kilometres. Microseisms occur as an increasing of seismic background noise between 2 and 20 s; in this range, primary and secondary peaks, at 5 and 14 s, are observed. Common broad-band seismic data, recorded with Romanian dense seismic

  7. Infrasound Generation from the Source Physics Experiments

    NASA Astrophysics Data System (ADS)

    Preston, L. A.; Schramm, K. A.; Jones, K. R.

    2015-12-01

    Understanding the acoustic and infrasound source generation mechanisms from underground explosions is of great importance for usage of this unique data type in non-proliferation activities. One of the purposes of the Source Physics Experiments (SPE), a series of underground explosive shots at the Nevada National Security Site (NNSS), is to gain an improved understanding of the generation and propagation of physical signals, such as seismic and infrasound, from the near to far field. Two of the SPE shots (SPE-1 and SPE-4') were designed to be small "Green's Function" sources with minimal spall or permanent surface deformation. We analyze infrasound data collected from these two shots at distances from ~300 m to ~1 km and frequencies up to 20 Hz. Using weather models based upon actual observations at the times of these sources, including 3-D variations in topography, temperatures, pressures, and winds, we synthesized full waveforms using Sandia's moving media acoustic propagation simulation suite. Several source mechanisms were simulated and compared and contrasted with observed waveforms using full waveform source inversion. We will discuss results of these source inversions including the relative roll of spall from these small explosions. 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.

  8. Integrated video and infrasound observations at Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Krzesni, D.; Johnson, J.; Kyle, P. R.

    2012-12-01

    Erebus volcano is ideally suited for infrasound studies because it produces frequent, discrete, short-duration Strombolian eruptions that generate simple, high-amplitude (10^3 - 10^4 Pa-m), high signal-to-noise, acoustic pulses. Some explosions have been recorded by a video camera situated 300 m from the lava lake. Here we analyze the infrasound signal recordings from 256 eruptions, 10 were accompanied by high-quality video. We have developed image processing scripts in MATLAB to measure the explosive expansion of eject in consecutive 30 fps video. An ellipse was fitted to the expanding surface, which begins as an intact bubble and then fragments into radially-projected ballistics. The volume of the magma bubble was estimated in each frame of the video and used to produce a synthetic infrasound wave. We assumed an acoustic monopole point source model where the volumetric acceleration was proportional to the radiated pressure waveform. In a comparison of synthetic and recorded infrasound we find a consistent match in both frequency and amplitude. The synthetic infrasound amplitude is generally greater than the amplitude of the observed infrasound. This suggests some non-linear decay in acoustic energy between the fluid ejection source and the infrasound recording sites. The infrasound signals were also analyzed to determine if a precursory pulse (or shoulder) in the waveforms, was related to distension of an unbroken magma bubble membrane prior to rupture. We examined the pressure slope (at the onset of an eruption) and the scaled asymmetry (of the bimodal pulses), and relate them to the initial magma overburden and source overpressure respectively. For significantly asymmetric infrasound pulses, with large rarefactions compared to initial compression, we speculate that rupture occurs for bubble slugs with very low overpressures.

  9. Sources of Infrasound events listed in IDC Reviewed Event Bulletin

    NASA Astrophysics Data System (ADS)

    Bittner, Paulina; Polich, Paul; Gore, Jane; Ali, Sherif; Medinskaya, Tatiana; Mialle, Pierrick

    2017-04-01

    Until 2003 two waveform technologies, i.e. seismic and hydroacoustic were used to detect and locate events included in the International Data Centre (IDC) Reviewed Event Bulletin (REB). The first atmospheric event was published in the REB in 2003, however automatic processing required significant improvements to reduce the number of false events. In the beginning of 2010 the infrasound technology was reintroduced to the IDC operations and has contributed to both automatic and reviewed IDC bulletins. The primary contribution of infrasound technology is to detect atmospheric events. These events may also be observed at seismic stations, which will significantly improve event location. Examples sources of REB events, which were detected by the International Monitoring System (IMS) infrasound network were fireballs (e.g. Bangkok fireball, 2015), volcanic eruptions (e.g. Calbuco, Chile 2015) and large surface explosions (e.g. Tjanjin, China 2015). Query blasts (e.g. Zheleznogorsk) and large earthquakes (e.g. Italy 2016) belong to events primarily recorded at seismic stations of the IMS network but often detected at the infrasound stations. In case of earthquakes analysis of infrasound signals may help to estimate the area affected by ground vibration. Infrasound associations to query blast events may help to obtain better source location. The role of IDC analysts is to verify and improve location of events detected by the automatic system and to add events which were missed in the automatic process. Open source materials may help to identify nature of some events. Well recorded examples may be added to the Reference Infrasound Event Database to help in analysis process. This presentation will provide examples of events generated by different sources which were included in the IDC bulletins.

  10. Urban Infrasound Observations - Examples from July 4th 2012

    NASA Astrophysics Data System (ADS)

    McComas, S.; Hayward, C.; Golden, P.; McKenna, M.; Simpson, C.

    2012-12-01

    Historical observations indicate that urban environments are rich in infrasound signals and thus provide the opportunity to characterize sources, monitor propagation path effects, and document diurnal and seasonal variability in the urban acoustical noise environment. If infrasound is to be used as viable signal for monitoring the urban environment and for identifying human and natural activities, the following key scientific issues must be examined: (1) What are the typical infrastructural sources of infrasound and their levels? (2) How saturated is the urban environment with infrasonic signals, i.e., do many signals propagate over long distances to reach a given sensor, or can individual sources be well differentiated? (3) Does infrasound provide new information to characterize rapidly evolving physical, cultural, economic, and military actions of interest? Each of these issues will be addressed with the acquisition and analysis of data from this observational study, including an analysis of the seasonal variation in infrasound noise and propagation effects. Such studies differ from typical infrasound work in that the propagation paths are short, i.e. ~1- 100 km, and signal frequencies can extend from the infrasound band to the low frequency acoustic band (100 Hz). We have begun a study to address some of the unique infrasound research questions and sources found in an urban environment. Our initial investigation of the data and a description of the identified noise and source signals are reported here. Three seismo-acoustic arrays were deployed on rooftops across the Southern Methodist University campus in Dallas, Texas, to characterize the urban infrasound environment. The first rooftop array, the Moody Coliseum, includes four elements at the corners of a 38m square and one element in the center. A seismometer is included at the central element. The second Multi-rooftop Array is spread across multiple building rooftops and has a 140m aperture. The third array

  11. A repeating secondary source of infrasound from the Wells, Nevada, earthquake sequence

    NASA Astrophysics Data System (ADS)

    Arrowsmith, Stephen J.; Burlacu, Relu; Whitaker, Rod; Randall, George

    2009-06-01

    The Wells, Nevada, earthquake of February 21, 2008, generated a complex seismo-acoustic wavefield. Epicentral infrasound was recorded at 5 seismo-acoustic arrays in Nevada, Utah, and Wyoming. In addition to epicentral infrasound, the earthquake triggered a secondary source of infrasound at the BGU array in Utah, which was also triggered by subsequent aftershocks. By applying simple constraints on the propagation of seismic and infrasound waves, we show that the secondary source is an isolated peak (‘Floating Island’) that appears to efficiently generate infrasound through the interaction with seismic surface waves. This hypothesized source location is broadly consistent with crosswind directions extracted from the Ground-to-Space (G2S) atmospheric model (for the appropriate time and source/receiver locations), although modeling the propagation of infrasound predicts this source location to be within the so-called ‘zone-of-silence’. In contrast to epicentral infrasound, secondary infrasound associated with the Wells, Nevada, earthquake sequence appears to be local to each array (i.e., not observed at multiple arrays). Secondary infrasonic arrivals observed at BGU are much higher in amplitude than epicentral arrivals, highlighting the importance of being able to clearly identify and separate epicentral and secondary arrivals for infrasonic event discrimination.

  12. Observed and predicted performance of the global IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Ceranna, L.; Landes, M.

    2012-04-01

    The International Monitoring System (IMS) infrasound network is being deployed to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Global-scale analyses of data recorded by this network indicate that the detection capability exhibits strong spatio-temporal variations. Previous studies estimated radiated acoustic source energy from remote infrasound observations using empirical yield-scaling relations, which account for the along-path stratospheric winds. Although the empirical wind correction reduces the variance in the explosive energy versus pressure relationship, large error remains in the yield estimates. Numerical modeling techniques are now widely employed to investigate the role of different factors describing atmospheric infrasound sources and propagation. Here we develop a theoretical attenuation relation from a large set of numerical simulations using the Parabolic Equation method. This relation accounts for the effects of the source frequency; geometrical spreading and dissipation; and realistic atmospheric specifications on the pressure wave attenuation. Compared with previous studies, the derived attenuation relation incorporates a more realistic physical description of infrasound propagation. By incorporating real ambient noise information at the receivers, we obtain the minimum detectable source amplitude in the frequency band of interest for detecting explosions. Empirical relations between the source spectrum and explosion yield are used to infer detection thresholds in tons of TNT equivalent. In the context of future verification of the CTBT, the obtained attenuation relation provides a more realistic picture of the spatio-temporal variability of the IMS network performance. The attenuation relation could also be used in the design and maintenance of an arbitrary infrasound monitoring network.

  13. Source Inversions of Volcano Infrasound: Mass Outflux and Force System for Transient Explosive Eruptions

    NASA Astrophysics Data System (ADS)

    Kim, K.; Fee, D.; Lees, J. M.; Yokoo, A.; Ruiz, M. C.

    2014-12-01

    Sources of volcano infrasound associated with explosive eruptions are typically modeled assuming an acoustic monopole and/or dipole. While the monopole represents the mass outflux of erupted materials, the dipole represents a force system acting in the source region during eruptions. Therefore, appropriate acoustic source inversions of volcano infrasound data can provide estimates of eruption parameters which are critical to understanding eruption dynamics. Reliability of the source parameters is dominantly controlled by the accuracy of the acoustic Green's functions between the source and receiver positions. Conventional source inversions of volcano infrasound, however, were typically performed using a simplified Green's function obtained in a free space or half space. This may result in intolerable errors in the source parameters, especially when the infrasound waveforms are significantly distorted by volcano topography and/or local atmospheric variability (i.e., layered velocity structure or wind). In this study we present a full waveform inversion technique for volcano infrasound using numerical Green's functions. A full 3-D Finite-Difference Time-Domain (FDTD) method accelerated with GPU is used to compute accurate Green's functions taking into account volcano topography and local atmospheric conditions. The presented method is applied to data recorded at Sakurajima volcano (Japan) and Tungurahua volcano (Ecuador), which provide a large volume of high-quality data recorded by azimuthally well-distributed stations within 2 -- 6 km distance of the volcanoes. We analyze infrasound signals associated with explosive eruptions exhibiting 1) distinct explosion waveforms followed by gas discharges and 2) strong anisotropic radiation patterns, which can be caused by either source directivity or topographic barriers/reflections. Here the role of topography in controlling the infrasound radiation is investigated through numerical modeling, and then the observed

  14. Imaging volcanic infrasound sources using time reversal mirror algorithm

    NASA Astrophysics Data System (ADS)

    Kim, Keehoon; Lees, Jonathan M.

    2015-09-01

    We investigate the capability of Time Reversal Mirror (TRM) algorithm to image local acoustic sources (<3.5 km) associated with complex, sustained volcanic eruptions. Accurate source localization for volcano infrasound (low-frequency acoustic waves) is often challenging due to pronounced volcanic topography and emergent arrivals of infrasound signals. While the accuracy of the conventional approaches (e.g. triangulation and semblance method) can be severely compromised by the complex volcanic settings, a TRM-based method may have the potential to properly image acoustic sources by the use of full waveform information and numerical modelling of the time-reversed wavefield. We apply the TRM algorithm to a pyroclastic-laden eruption (sustained for ˜60 s) at Santiaguito Volcano, Guatemala, and show that an ordinary TRM operation can undergo significant reduction of its focusing power due to strong topographic propagation effects (e.g. reflection and diffraction). We propose a weighted imaging condition to compensate for complicated transmission loss of the time-reversed wavefield and demonstrate that the presented condition significantly improves the focusing quality of TRM in the presence of complex topography. The consequent TRM source images exhibit remarkable agreement with the visual observation of the eruption implying that the TRM method with a proper imaging condition can be used to localize and track acoustic sources associated with complex volcanic eruptions.

  15. Infrasound Observations of the Massive Landslide at Bingham Canyon Copper Mine

    NASA Astrophysics Data System (ADS)

    Hale, J. M.; Arrowsmith, S.; Burlacu, R.; Hayward, C.; Pankow, K. L.

    2013-12-01

    On 10 April 2013 approximately 55 million m3 of rock collapsed from the northeastern wall of the approximately one-kilometer deep open-pit Bingham Canyon copper mine near Salt Lake City, Utah, generating clear seismic and infrasound signals. The material released in two sudden rock avalanches separated in time by about 1.5 hours. The magnitudes for the two slides were determined to be ML 2.5 and 2.4 and MSW 5.0 and 4.9, respectively. Seismic signals with durations approaching two minutes from both rock avalanches were recorded on stations of the University of Utah (UU) regional seismic network and other networks at distances of ~6 to greater than 400 km. In addition, the first event was recorded on seven UU infrasound arrays at distances of ~13 - 400 km and the second at five infrasound arrays between ~57 and 400 km distance. Comparison of the seismograms from the two slides show differences in the long-period energy. There are also clear differences in the infrasound observations. For example, at the closest array recording both slides, the duration of the infrasound signal for the first slide is much longer than for the second slide. In addition, infrasound attributed to the first rock avalanche resulted in multiple arrival observations at the three most distant arrays, while only one array had multiple arrivals for the latter event. For the five infrasound arrays, with detections for both rock avalanches, we look for signal differences by cataloging duration, amplitude, azimuth, dominant period, correlation coefficients, group and trace velocity. In addition, propagation modeling through ground-to-space (G2S) profiles will be performed to determine if atmospheric differences can account for the varying infrasound observations, and the source of the infrasound signal will be located using the Bayesian Infrasonic Source Location procedure. With a wealth of geophysical data we aim to determine if the seismic and infrasound signals have a common source and if the

  16. Source location of the 19 February 2008 Oregon bolide using seismic networks and infrasound arrays

    NASA Astrophysics Data System (ADS)

    Walker, Kristoffer T.; Hedlin, Michael A. H.; de Groot-Hedlin, Catherine; Vergoz, Julien; Le Pichon, Alexis; Drob, Douglas P.

    2010-12-01

    On 19 February 2008 a bolide traveled across the sky along a southern trajectory ending in a terminal burst above Oregon. The event was well recorded by the USArray, other seismic networks, four infrasound arrays, and several video cameras. We compare the results of locating the burst using these different sensor networks. Specifically, we reverse time migrate acoustic-to-seismic coupled signals recorded by the USArray out to 800 km range to image the source in 2-D space and time. We also apply a grid search over source altitude and time, minimizing the misfit between observed and predicted arrival times using 3-D ray tracing with a high-resolution atmospheric velocity model. Our seismic and video results suggest a point source rather than a line source associated with a hypersonic trajectory. We compare the seismic source locations to those obtained by using different combinations of observed infrasound array signal back azimuths and arrival times. We find that all locations are consistent. However, the seismic location is more accurate than the infrasound locations due to the larger number of seismic sensors, a more favorable seismic source-receiver geometry, and shorter ranges to the seismometers. For the infrasound array locations, correcting for the wind improved the accuracy, but implementing arrival times while increasing the precision reduced the accuracy presumably due to limitations of the source location method and/or atmospheric velocity model. We show that despite known complexities associated with acoustic-to-seismic coupling, aboveground infrasound sources can be located with dense seismic networks with remarkably high accuracy and precision.

  17. Infrasound signals from events at the DPRK test site: observations and modeling results

    NASA Astrophysics Data System (ADS)

    Koch, Karl; Pilger, Christoph

    2017-04-01

    Over the last ten years North Korea announced underground nuclear test explosions at its Punggyi-ri test site in October 2006, May 2009, February 2013 as well as in January and September 2016. For the test in February 2013 infrasound arrivals are clearly seen in recordings at IMS station IS45 in Russia. These have been associated to the event in the Reviewed Event Bulletin (REB) along with an arrival for IMS station IS30, which appears hidden in the background noise of the waveforms. Even before these infrasound arrivals were detected, there have been reports from infrasound signals observed at a network of national infrasound stations in South Korea for the May 2009 events. These stations subsequently were also reported to have detected the 2013 event acoustically. More recently it was found for IS45 that it may have detections from the January 2016 underground nuclear explosion. Based on these reports we undertook a comprehensive study and searched for infrasound arrivals in the data of two IMS stations, IS30 and IS45, that could have originated from near-source conversion near the primary nuclear explosion source. For all events analyzed using the frequency-wavenumber (F-K) technique, we find infrasound signals, except for the events in 2009 and September 2016, that can be attributed to the source at the test site, in terms of appropriate arrival directions and apparent velocities. For the 2009 event we find a late acoustic arrival at IS45 corresponding to a previously observed arrival arriving early at South Korean stations, which are located in the opposite direction of IS45. We apply propagation modeling using ray tracing and parabolic equation calculations in order to verify all observed infrasound detections at the IMS stations as well as reported arrivals from a station in South Korea. Finally we also examined the case of the 12 May 2010 event, for which we find weak or spurious detections, but which we can model sufficiently well, so that we can not rule

  18. Automatic Infrasound Detection and Location of Sources in the western US

    NASA Astrophysics Data System (ADS)

    Park, J.; Arrowsmith, S.; Hayward, C.; Stump, B. W.

    2012-12-01

    Infrasound event catalogs can be used to study the characteristics of events as well as the time varying nature of the atmosphere. Additionally, these catalogs can be used to identify sources that repeat and thus provide ground truth for atmospheric studies. We focus on the production of a western US regional infrasound catalog for the time period of April 2011 to March 2012. Data from the University of Utah Seismograph Stations (UUSS) infrasonic arrays are supplemented with data from three additional infrasound arrays in Nevada. An automated detection procedure was applied to the observations based on an adaptive F-detector (Arrowsmith et al., 2009). The detection results document significant seasonal variations in time and space; detections during the winter tend to produce higher correlations relative to those from the summer, and a seasonal variation in azimuth is observed. These results indicate that the bulletin is seasonally variable. Association of detections and event localization was done utilizing the Bayesian infrasonic source location procedure (BISL, Modrak et al., 2010), accounting for unknown atmospheric propagation effects by adding a random component to the infrasonic group velocity. The resulting infrasonic catalog consists of 963 events for the one-year time period with indication of repeated events from a number of locations. The distribution of infrasound events in this study is well matched with the infrasound hot spots identified by Walker et al. (2011) which were based on a back projection procedure applied to seismic signals from USArray Transportable Array. There are common concentrations of events in both catalogs that include New Bomb in Nevada, Utah Test and Training Range (UTTR), and Dugway Proving Ground in Utah, as well as broader areas in central Nevada and southwest Idaho. The two bulletins document that the vast majority of events occur during work hours, suggesting they are related to human activities.

  19. Linking Volcano Infrasound Observations to Conduit Processes for Vulcanian Eruptions

    NASA Astrophysics Data System (ADS)

    Watson, L. M.; Dunham, E. M.; Almquist, M.; Mattsson, K.; Ampong, K.

    2016-12-01

    Volcano infrasound observations have been used to infer a range of eruption parameters, such as volume flux and exit velocity, with the majority of work focused on subaerial processes. Here, we propose using infrasound observations to investigate the subsurface processes of the volcanic system. We develop a one-dimensional model of the volcanic system, coupling an unsteady conduit model to a description of a volcanic jet with sound waves generated by the expansion of the jet. The conduit model describes isothermal two-phase flow with no relative motion between the phases. We are currently working on including crystals and adding conservation of energy to the governing equations. The model captures the descent of the fragmentation front into the conduit and approaches a steady state solution with choked flow at the vent. The descending fragmentation front influences the time history of mass discharge from the vent, which is linked to the infrasound signal through the volcanic jet model. The jet model is coupled to the conduit by conservation of mass, momentum, and energy. We compare simulation results for a range of models of the volcanic jet, ranging in complexity from assuming conservation of volume, as has been done in some previous infrasound studies, to solving the Euler equations for the surrounding compressible atmosphere and accounting for entrainment. Our model is designed for short-lived, impulsive Vulcanian eruptions, such as those seen at Sakurajima Volcano, with activity triggered by a sudden drop in pressure at the top of the conduit. The intention is to compare the simulated signals to observations and to devise an inverse procedure to enable inversion for conduit properties.

  20. A repeating source of infrasound from the Wells, Nevada earthquake sequence

    SciTech Connect

    Arrowsmith, Stephen J.; Whitaker, Rod; Randall, George; Burlacu, Relu

    2009-01-01

    The Wells, Nevada earthquake of February 21, 2008, generated a complex seismoacoustic wakefield. In addition to epicentral infrasound, the earthquake triggered a secondary source of infrasound, which was also initiated by subsequent aftershocks. By applying simple constraints on the propagation of seismic and infrasound waves, we show that the secondary source is an isolated peak that appears to efficiently generate infrasound through the interaction with seismic surface waves. By measuring peak-to-peak amplitudes of epicentral and secondary arrivals and correcting them for the effects of distance and winds, we find that epicentral arrivals lit with empirical relationships of Mutschlecner and Whitaker (2005) and Le Pichon et al. (2006), which form the basis for a proposed infrasound discriminant (Anderson et al., Pers. Comm.). In contrast, the secondary arrivals are much higher in amplitude, highlighting the importance of being able to separate epicentral and secondary arrivals for infrasonic event discrimination.

  1. Volcano Infrasound

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Fee, D.; Matoza, R. S.

    2013-12-01

    Open-vent volcanoes generate prodigious low frequency sound waves that tend to peak in the infrasound (<20 Hz) band. These long wavelength (> ~20 m) atmospheric pressure waves often propagate long distances with low intrinsic attenuation and can be well recorded with a variety of low frequency sensitive microphones. Infrasound records may be used to remotely monitor eruptions, identify active vents or track gravity-driven flows, and/or characterize source processes. Such studies provide information vital for both scientific study and volcano monitoring efforts. This presentation proposes to summarize and standardize some of the terminology used in the still young, yet rapidly growing field of volcano infrasound. Herein we suggest classification of typical infrasound waveform types, which include bimodal pulses, blast (or N-) waves, and a variety of infrasonic tremors (including broadband, harmonic, and monotonic signals). We summarize various metrics, including reduced pressure, intensity, power, and energy, in which infrasound excess pressures are often quantified. We also describe the spectrum of source types and radiation patterns, which are typically responsible for recorded infrasound. Finally we summarize the variety of propagation paths that are common for volcano infrasound radiating to local (<10 km), regional (out to several hundred kilometers), and global distances. The effort to establish common terminology requires community feedback, but is now timely as volcano infrasound studies proliferate and infrasound becomes a standard component of volcano monitoring.

  2. Use of Numerical Weather Research and Forecasting Specifications in Infrasound Propagation Modeling of Local and Regional Sources - Preliminary Investigations

    NASA Astrophysics Data System (ADS)

    Nava, S.; Masters, S. E.; Norris, D.

    2009-12-01

    High resolution characterization of the lower atmosphere is an important aspect of infrasound propagation modeling of local and regional sources. Rawinsonde weather balloons can be used to obtain such information, but may be impractical or unavailable at the time and location of interest, and do not capture spatial variability that may be important over regional ranges. In this study, we explore the utility of the Weather Research and Forecasting (WRF) Model, a state-of-the-science mesoscale numerical weather prediction system used in operational forecasting and atmospheric research (http://wrf-model.org). A ground truth database of analyst-confirmed mining and military disposal explosions recorded on an infrasound array located near Salt Lake City, Utah (USA), with source-to-receiver distances ranges from 15-200 km, forms the basis of this study. Of primary interest is infrasound propagation within the so-called zone of silence. Cases were identified in which infrasound detections were and were not observed from the same source location. It is assumed that the method of source detonation was similar and the dynamic atmosphere was the only variable affecting the observability. The WRF-model was executed to produce high resolution spatial and temporal wind and temperature fields for input into infrasound propagation models. The WRF simulations extended to 16-20 km altitude, and were configured using nested domains with horizontal spatial resolution of approximately 1.8 km and temporal output resolution of 15 minutes. Each simulation was initialized with the Global Forecast System (GFS) analysis approximately 12-18 hours before the infrasound event of interest and calculations continued for 24 hours. Local observed surface, upper air, radar, and rawinsonde data were used to judge if the WRF model fields were reasonable and matched the actual weather conditions. Ray trace, parabolic equation, and time-domain parabolic equation propagation predictions were computed

  3. Infrasound, Its Sources and Its Effects on Man

    DTIC Science & Technology

    1976-05-01

    that are harmful or even audible to man. Thus infrasound exposure is not one of mankinds more press- ling environmental problems. g SECURITY...unwarranted conclusions infrasound is not one of mankiuds more pressing about the effects of infrasound on man. The environmental problems. upper frequency... health and welfare is via all those many factors above 20 Hz could be eliminated, 1 baiieve there that make up the annoyance response. Now it is would be

  4. Atmospheric Model Effects on Infrasound Source Inversion from the Source Physics Experiments

    NASA Astrophysics Data System (ADS)

    Preston, L. A.; Aur, K. A.

    2016-12-01

    The Source Physics Experiments (SPE) consist of a series of underground explosive shots at the Nevada National Security Site (NNSS) designed to gain an improved understanding of the generation and propagation of physical signals in the near and far field. Characterizing the acoustic and infrasound source mechanism from underground explosions is of great importance in non-proliferation activities. To this end we perform full waveform source inversion of infrasound data collected from SPE shots at distances from 300 m to 1 km and frequencies up to 20 Hz. Our method requires estimating the state of the atmosphere at the time of each shot, computing Green's functions through these atmospheric models, and subsequently inverting these signals in the frequency domain to obtain a source time function. To estimate the state of the atmosphere at the time of the shot, we utilize two different datasets: North American Regional Reanalysis data, a comprehensive but lower resolution dataset, and locally obtained sonde and surface weather observations. We synthesize Green's functions through these atmospheric models using Sandia's moving media acoustic propagation simulation suite. These models include 3-D variations in topography, temperature, pressure, and wind. We will compare and contrast the atmospheric models derived from the two weather datasets and discuss how these differences affect computed source waveforms and contribute to modeling uncertainty. 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.

  5. Remote infrasound monitoring of Mount Etna: Observed and predicted network detection capability

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Le Pichon, Alexis; Marchetti, Emanuele; Ripepe, Maurizio; Kallel, Mohamed; Ceranna, Lars

    2013-04-01

    Volcanic eruptions are unique and valuable calibrating sources of infrasonic waves worldwide detected by the International Monitoring System (IMS) of the Comprehensive nuclear Test Ban Treaty Organization (CTBTO) and other experimental stations. Building a comprehensive database of volcanic signals is likely to help the scientific community to better characterize eruptive sequences and may help to prevent eruption disasters while on a longer term mitigate the impact of ash clouds on aviation. In this study, we assess the detection capability of the existing infrasound network to remotely detect the eruptive activity of Mount Etna with a high level of confidence, and predict the performance of the future ARISE infrastructure network (Atmospheric dynamics InfraStructure in Europe). This well-instrumented volcano offers a unique opportunity to validate attenuation models using multiyear near-and-far field recordings. The seasonal trend in the number of detections of Etna at the IS48 IMS station (Tunisia) is correlated to fine temporal fluctuations of the stratospheric waveguide structure. The modeling results are consistent with the observed detection capability of the existing network. In summer, during the downwind season, a minimum detectable amplitude of ~10 Pa at a reference distance of 1 km from the source is predicted. In winter, when upwind propagation occurs, detection thresholds increase up to ~100 Pa. When adding four experimental arrays to the existing IMS network, thresholds decrease down to ~20 Pa in winter. The simulation results provide here a realistic description of long-range infrasound propagation and allow predicting fine temporal fluctuations in the European infrasound network performance with potential application for civil aviation safety.

  6. Infrasound and SO2 Observations of the 2011 Explosive Eruption of Nabro Volcano, Eritrea

    NASA Astrophysics Data System (ADS)

    Fee, D.; Carn, S. A.; Prata, F.

    2011-12-01

    Nabro volcano, Eritrea erupted explosively on 12 June 2011 and produced near continuous emissions and infrasound until mid-July. The eruption disrupted air traffic and severely affected communities in the region. Although the eruption was relatively ash-poor, it produced significant SO2 emissions, including: 1) the highest SO2 column ever retrieved from space (3700 DU), 2) >1.3 Tg SO2 mass on 13 June, and 3) >2 Tg of SO2 for the entire eruption, one of the largest eruptive SO2 masses produced since the 1991 eruption of Mt. Pinatubo. Peak emissions reached well into the stratosphere (~19 km). Although the 12 June eruption was preceded by significant seismicity and clearly detected by satellite sensors, Nabro volcano is an understudied volcano that lies in a remote region with little ground-based monitoring. The Nabro eruption also produced significant infrasound signals that were recorded by two infrasound arrays: I19DJ (Djibouti, 264 km) and I32KE (Kenya, 1708 km). The I19DJ infrasound array detected the eruption with high signal-noise and provides the most detailed eruption chronology available, including eruption onset, duration, changes in intensity, etc. As seen in numerous other studies, sustained low frequency infrasound from Nabro is coincident with high-altitude emissions. Unexpectedly, the eruption also produced hundreds of short-duration, impulsive explosion signals, in addition to the sustained infrasonic jetting signals more typical of subplinian-plinian eruptions. These explosions are variable in amplitude, duration, and often cluster in groups. Here we present: 1) additional analyses, classification, and source estimation of the explosions, 2) infrasound propagation modeling to determine acoustic travel times and propagation paths, 3) detection and characterization of the SO2 emissions using the Ozone Monitoring Instrument (OMI) and Spin Enhanced Visible and Infra-Red Instrument (SEVIRI), and 4) a comparison between the relative infrasound energy and

  7. Seismic and infrasound observations of recent explosive events at Marapi Volcano in Western Sumatra

    NASA Astrophysics Data System (ADS)

    Taisne, B.; Tan, C. T.; Perttu, A. B.; Nurfiani, D.; Hidayat, D.; Suantika, G.; Gunawan, H.; Patria, C.; Adi, S.; Triastuti, H.; K.

    2016-12-01

    A small eruption was reported at Marapi Volcano in Western Sumatra on the evening of November 14, 2015. Based on seismic records this eruption occurred approximately 15:33 UTC. There were no visual nor satellite observations of an associated ash plume. The eruption was recorded on the local seismic network, as well as the regional Singapore Infrasound Array. Thanks to the ground-coupled air wave associated with this explosion infrasound was also observed on the local seismic network. Using waveform inversion, source parameters that best fit the observations were for a depth of 900 meters. The depth of the explosion was also estimated using the seismic and acoustic arrival times on the local network giving a depth from 400 to 1000 meters with the highest probability at 700 meters below the crater. Subtle changes in the frequency content of the seismic signal were observed 3 hours prior to the explosion using a Self-Organizing Map. To further the understanding of the behavior of Marapi volcano, the strong November, 14th, 2015 event has been compared with November 2014, April and August 2015 as well as July 2016 events.

  8. Local and remote infrasound from explosive volcanism

    NASA Astrophysics Data System (ADS)

    Matoza, R. S.; Fee, D.; LE Pichon, A.

    2014-12-01

    Explosive volcanic eruptions can inject large volumes of ash into heavily travelled air corridors and thus pose a significant societal and economic hazard. In remote volcanic regions, satellite data are sometimes the only technology available to observe volcanic eruptions and constrain ash-release parameters for aviation safety. Infrasound (acoustic waves ~0.01-20 Hz) data fill this critical observational gap, providing ground-based data for remote volcanic eruptions. Explosive volcanic eruptions are among the most powerful sources of infrasound observed on earth, with recordings routinely made at ranges of hundreds to thousands of kilometers. Advances in infrasound technology and the efficient propagation of infrasound in the atmosphere therefore greatly enhance our ability to monitor volcanoes in remote regions such as the North Pacific Ocean. Infrasound data can be exploited to detect, locate, and provide detailed chronologies of the timing of explosive volcanic eruptions for use in ash transport and dispersal models. We highlight results from case studies of multiple eruptions recorded by the International Monitoring System and dedicated regional infrasound networks (2008 Kasatochi, Alaska, USA; 2008 Okmok, Alaska, USA; 2009 Sarychev Peak, Kuriles, Russian Federation; 2010 Eyjafjallajökull, Icleand) and show how infrasound is currently used in volcano monitoring. We also present progress towards characterizing and modeling the variability in source mechanisms of infrasound from explosive eruptions using dedicated local infrasound field deployments at volcanoes Karymsky, Russian Federation and Sakurajima, Japan.

  9. First observations of sprites in the eastern Mediterranean using the Israeli infrasound network

    NASA Astrophysics Data System (ADS)

    Applbaum, David; Price, Colin; Ben Horin, Yochai; Yair, Yoav

    2014-05-01

    As outlined by Farges et al (2005) as part of the Sprite2003 campaign in Europe, sprites at close range (less than a few hundred km) exhibit a unique signal in infrasound. This signal consists of an 'inverted chirp,' lasting up to several minutes and in which the higher frequencies arrive prior to the lower frequencies. The ILAN (Imaging of Lightning and Nocturnal Flashes) science team at Tel Aviv University maintains a database of optically observed sprites occurring within a few hundred kilometers of the Mediterranean coast of Israel. Using the observed azimuths of these sprites' locations with respect to the detectors, combined with an acoustic propagation model and the observed delays associated with propagation of the signals between the sprites and the infrasound arrays, we present here observations of several sprites that are consistent with the observations made by Farges et al. These constitute the first observations of sprites made using the Israeli infrasound network.

  10. Modeling propagation of infrasound signals observed by a dense seismic network.

    PubMed

    Chunchuzov, I; Kulichkov, S; Popov, O; Hedlin, M

    2014-01-01

    The long-range propagation of infrasound from a surface explosion with an explosive yield of about 17.6 t TNT that occurred on June 16, 2008 at the Utah Test and Training Range (UTTR) in the western United States is simulated using an atmospheric model that includes fine-scale layered structure of the wind velocity and temperature fields. Synthetic signal parameters (waveforms, amplitudes, and travel times) are calculated using parabolic equation and ray-tracing methods for a number of ranges between 100 and 800 km from the source. The simulation shows the evolution of several branches of stratospheric and thermospheric signals with increasing range from the source. Infrasound signals calculated using a G2S (ground-to-space) atmospheric model perturbed by small-scale layered wind velocity and temperature fluctuations are shown to agree well with recordings made by the dense High Lava Plains seismic network located at an azimuth of 300° from UTTR. The waveforms of calculated infrasound arrivals are compared with those of seismic recordings. This study illustrates the utility of dense seismic networks for mapping an infrasound field with high spatial resolution. The parabolic equation calculations capture both the effect of scattering of infrasound into geometric acoustic shadow zones and significant temporal broadening of the arrivals.

  11. West Texas array experiment: Noise and source characterization of short-range infrasound and acoustic signals, along with lab and field evaluation of Intermountain Laboratories infrasound microphones

    NASA Astrophysics Data System (ADS)

    Fisher, Aileen

    The term infrasound describes atmospheric sound waves with frequencies below 20 Hz, while acoustics are classified within the audible range of 20 Hz to 20 kHz. Infrasound and acoustic monitoring in the scientific community is hampered by low signal-to-noise ratios and a limited number of studies on regional and short-range noise and source characterization. The JASON Report (2005) suggests the infrasound community focus on more broad-frequency, observational studies within a tactical distance of 10 km. In keeping with that recommendation, this paper presents a study of regional and short-range atmospheric acoustic and infrasonic noise characterization, at a desert site in West Texas, covering a broad frequency range of 0.2 to 100 Hz. To spatially sample the band, a large number of infrasound gauges was needed. A laboratory instrument analysis is presented of the set of low-cost infrasound sensors used in this study, manufactured by Inter-Mountain Laboratories (IML). Analysis includes spectra, transfer functions and coherences to assess the stability and range of the gauges, and complements additional instrument testing by Sandia National Laboratories. The IMLs documented here have been found reliably coherent from 0.1 to 7 Hz without instrument correction. Corrections were built using corresponding time series from the commercially available and more expensive Chaparral infrasound gauge, so that the corrected IML outputs were able to closely mimic the Chaparral output. Arrays of gauges are needed for atmospheric sound signal processing. Our West Texas experiment consisted of a 1.5 km aperture, 23-gauge infrasound/acoustic array of IMLs, with a compact, 12 m diameter grid-array of rented IMLs at the center. To optimize signal recording, signal-to-noise ratio needs to be quantified with respect to both frequency band and coherence length. The higher-frequency grid array consisted of 25 microphones arranged in a five by five pattern with 3 meter spacing, without

  12. Statistical analysis of infrasound signatures in airglow observations: Indications for acoustic resonance

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Schmidt, Carsten; Bittner, Michael

    2013-02-01

    The detection of infrasonic signals in temperature time series of the mesopause altitude region (at about 80-100 km) is performed at the German Remote Sensing Data Center of the German Aerospace Center (DLR-DFD) using GRIPS instrumentation (GRound-based Infrared P-branch Spectrometers). Mesopause temperature values with a temporal resolution of up to 10 s are derived from the observation of nocturnal airglow emissions and permit the identification of signals within the long-period infrasound range.Spectral intensities of wave signatures with periods between 2.5 and 10 min are estimated applying the wavelet analysis technique to one minute mean temperature values. Selected events as well as the statistical distribution of 40 months of observation are presented and discussed with respect to resonant modes of the atmosphere. The mechanism of acoustic resonance generated by strong infrasonic sources is a potential explanation of distinct features with periods between 3 and 5 min observed in the dataset.

  13. Infrasound Monitoring of the Volcanic Activities of Japanese Volcanoes in Korea

    NASA Astrophysics Data System (ADS)

    Lee, H. I.; Che, I. Y.; Shin, J. S.

    2015-12-01

    Since 1999 when our first infrasound array station(CHNAR) has been installed at Cheolwon, Korea Institute of Geoscience and Mineral Resources(KIGAM) is continuously observing infrasound signals with an infrasound array network, named KIN(Korean Infrasound Network). This network is comprised of eight seismo-acoustic array stations(BRDAR, YPDAR, KMPAR, CHNAR, YAGAR, KSGAR, ULDAR, TJIAR). The aperture size of the smallest array is 300m and the largest is about 1.4km. The number of infrasound sensors are between 4(TJIAR) and 18(YAGAR), and 1~5 seismometers are collocated with infrasound sensors. Many interesting infrasound signals associated with different type of sources, such as blasting, large earthquake, bolide, volcanic explosion are detected by KIN in the past 15 years. We have analyzed the infrasound signals possibly associated with the japanese volcanic explosions with reference to volcanic activity report published by Japanese Meteorological Agency. Analysis results of many events, for example, Asama volcano explosion in 2004 and Shinmoe volcano in 2011, are well matched with the official report. In some cases, however, corresponding infrasound signals are not identified. By comparison of the infrasound signals from different volcanoes, we also found that the characteristics of signals are distinguishing. It may imply that the specific volcano has its own unique fingerprint in terms of infrasound signal. It might be investigated by long-term infrasound monitoring for a specific volcano as a ground truth generating repetitive infrasound signal.

  14. Infrasound from the Explosion Sources in the 1-200 km at UTTR

    NASA Astrophysics Data System (ADS)

    Kim, T. S.; Stump, B. W.; Kang, I. B.; Hayward, C.

    2009-04-01

    The propagation of infrasound in the standard atmospheric model is not predicted at the distances less than 250 km, which is called "zone of silence" (Mckenna, 2005). In empirical studies, however, infrasound signals can be recorded in this "shadow zone" (Reed, 1969; Che et al., 2002; Pinsky et al. 2006; Evers et al., 2007) even though the physics of infrasound propagation at this distance range is not well known due to limitations restricted by the quality of ground truth, station distribution and the lack of atmospheric profile. The experiment in Utah performed in August, 2007 had high quality ground truths (G0) from four rocket motors and a dense deployment of infrasound gauges including six arrays and thirteen single stations at distances from 100 meters over 210 kilometers. The atmospheric profile from the surface to about 25 km at the maximum height gave us an opportunity to access the variations of local atmospheric condition and model the infrasound propagation. To understand the characteristics of propagation path effect on the travel time and waveform of infrasound signals, systematic analysis on group and phase velocities, amplitude variation and atmospheric profile was performed. Based on the analysis, the infrasonic arrivals were classified into two groups: The arrivals at the distance less than 100 km (local arrivals) and those between 150 and 210 km (regional arrivals). The estimates of group velocity at local distances are around 350 m/s while those of regional distances vary from 280 to 300 m/s. The mean phase velocity at local distance range is 359 ± 9.8 m/s which is near to the speed of sound at the surface while that of regional distance is 386 ± 7.6 m/s, which can be expected from the turning rays from the stratosphere or thermosphere. The Utah observations also demonstrate that infrasound amplitude does not decay at local distances around 50 km. The PE modeling explains partially that observed acoustic arrivals and focusing of amplitude at

  15. Modelling infrasound signal generation from two underground explosions at the Source Physics Experiment using the Rayleigh integral

    NASA Astrophysics Data System (ADS)

    Jones, Kyle R.; Whitaker, Rodney W.; Arrowsmith, Stephen J.

    2015-02-01

    We use the Rayleigh integral (RI) as an approximation to the Helmholtz-Kirchoff integral to model infrasound generation and propagation from underground chemical explosions at distances of 250 m out to 5 km as part of the Source Physics Experiment (SPE). Using a sparse network of surface accelerometers installed above ground zero, we are able to accurately create synthetic acoustic waveforms and compare them to the observed data. Although the underground explosive sources were designed to be symmetric, the resulting seismic wave at the surface shows an asymmetric propagation pattern that is stronger to the northeast of the borehole. This asymmetric bias may be attributed to the subsurface geology and faulting of the area and is observed in the acoustic waveforms. We compare observed and modelled results from two of the underground SPE tests with a sensitivity study to evaluate the asymmetry observed in the data. This work shows that it is possible to model infrasound signals from underground explosive sources using the RI and that asymmetries observed in the data can be modelled with this technique.

  16. The European Infrasound Bulletin

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars; Ross, J. Ole; Vergoz, Julien; Le Pichon, Alexis; Mialle, Pierrick

    2017-04-01

    The European Infrasound Bulletin highlights infrasound activity produced by mostly anthropogenic sources, recorded all over Europe and collected in the course of the ARISE project (Atmospheric dynamics Research InfraStructure in Europe). Data includes high frequency (>0.7 Hz) infrasound detections of 24 European infrasound arrays from 9 different national institutions (BGR, CEA, IRF, NORSAR, KNMI, UNIFI, IAP-Prague, NIEP, SOREQ) complemented with CTBT IMS infrasound stations. Data was acquired during 16 years of operation (from 2000 to 2015), and processed to identify and localize about 48.000 infrasound events within Europe (20°W-40°E, 30°N-72°N). The source location of these events was derived by combining at least two corresponding station detections per event. Comparisons to ground-truth sources, as e.g. Scandinavian mining activity, are provided. Relocation is performed using ray-tracing methods to estimate celerity and back-azimuth corrections based on either HWM-07/MSISE-00 climatologies or actual ECMWF wind and temperature values for each event. This study focuses on repeating infrasound events (e.g. mining blasts and supersonic flights) and on the seasonal, weekly and diurnal variation of the infrasonic activity of sources in Europe. Estimations of the detection and location capability and accuracy will be given in the course of this study to achieve a comprehensive picture of the activity of infrasound sources and capability of infrasound station in Europe.

  17. Magnetic infrasound sensor

    DOEpatents

    Mueller, Fred M.; Bronisz, Lawrence; Grube, Holger; Nelson, David C.; Mace, Jonathan L.

    2006-11-14

    A magnetic infrasound sensor is produced by constraining a permanent magnet inside a magnetic potential well above the surface of superconducting material. The magnetic infrasound sensor measures the position or movement of the permanent magnet within the magnetic potential well, and interprets the measurements. Infrasound sources can be located and characterized by combining the measurements from one or more infrasound sensors. The magnetic infrasound sensor can be tuned to match infrasound source types, resulting in better signal-to-noise ratio. The present invention can operate in frequency modulation mode to improve sensitivity and signal-to-noise ratio. In an alternate construction, the superconductor can be levitated over a magnet or magnets. The system can also be driven, so that time resolved perturbations are sensed, resulting in a frequency modulation version with improved sensitivity and signal-to-noise ratio.

  18. Tactical Infrasound

    DTIC Science & Technology

    2005-05-01

    appeared on their infrasound detector at the Lamont- Doherty observatory on the palisades above the Hudson River was generated by the Tappan Zee bridge ...Impulsive sources ..................... 14 3.2.3 Steady sources: bridges and structures ......... 15 3.3 Implications for the design of sonic detection...are currently too small (within the US) to produce a healthy and vibrant flow of new ideas, new implementations, and new people. The DoD would derive

  19. Infrasound research of volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Marchetti, Emanuele; Ripepe, Maurizio

    2016-04-01

    Volcanic eruptions are efficient sources of infrasound produced by the rapid perturbation of the atmosphere by the explosive source. Being able to propagate up to large distances from the source, infrasonic waves from major (VEI 4 or larger) volcanic eruptions have been recorded for many decades with analogue micro-barometers at large regional distances. In late 1980s, near-field observations became progressively more common and started to have direct impact on the understanding and modeling of explosive source dynamics, to eventually play a primary role in volcano research. Nowadays, infrasound observation from a large variety of volcanic eruptions, spanning from VEI 0 to VEI 5 events, has shown a dramatic variability in terms of signature, excess pressure and frequency content of radiated infrasound and has been used to infer complex eruptive source mechanisms for the different kinds of events. Improved processing capability and sensors has allowed unprecedented precise locations of the explosive source and is progressively increasing the possibility to monitor volcanoes from distant records. Very broadband infrasound observations is also showing the relation between volcanic eruptions and the atmosphere, with the eruptive mass injection in the atmosphere triggering acoustic-gravity waves which eventually might control the ash dispersal and fallout.

  20. Determination and Statistical Analysis of Infrasound Sources Near Socorro, New Mexico

    NASA Astrophysics Data System (ADS)

    Larson, T.; Lees, J. M.; Bowman, D. C.; Jones, K. R.

    2014-12-01

    Data collected from 2010 to 2014 at a seismo-acoustic array located outside Socorro, New Mexico provides the grounds for investigating atmospheric radiation of acoustic waves in the area. We extracted 698 impulsive signals (less than five seconds duration) as well as numerous longer period signals, likely trains or other vehicular noise in the region. Using arrival time differences, we derived three-dimensional incidence vectors of infrasound arrivals by calculating azimuth and inclination angles for a sorted group of 661 well-recorded impulsive signals (179 in 2010, 220 in 2012, 262 in 2013). During this period, impulsive sources arrive at the array from an average azimuth angle of 272.4 degrees. Two main clusters of events can be seen each year: the densest cluster spans the azimuth range 250.96-277.18 degrees, while the second cluster spans 294.33-336.35 degrees. Inclinations for both of these clusters are relatively low, as the main cluster spans 16.1-24.68 degrees and the second spans 4.69-18.44 degrees. The main cluster corresponds to the location of The Energetic Materials Research and Testing Center (EMRTC), which detonates regularly scheduled explosions and is located at an azimuth of 266 degrees with respect to the array. The second cluster lies to the north of the EMRTC range, but the source of these signals is unknown and requires further investigation. Signals associated with other sources, most likely mining explosions, appear each year emanating from south of EMRTC. Additionally, two minor clusters at low azimuth angles and high inclinations are observed, possibly originating from a number of sites including Kirtland Air Force Base, Sandia National Laboratories, and White Sands Missile Range. Waveform cluster analysis suggests distinct waveform similarity associated with specific sources.

  1. Infrasound from volcanic rockfalls

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey B.; Ronan, Timothy J.

    2015-12-01

    Proximal infrasound arrays can robustly track rapidly moving gravity-driven mass wasting, which occurs commonly at erupting volcanoes. This study reports on detection, localization, and quantification of frequent small rockfalls and infrequent pyroclastic density currents descending the southeast flanks of Santiaguito's active Caliente Dome in January of 2014. Such activities are identified as moving sources, which descend several hundred meters at bulk flow speeds of up to ~10 m/s, which is considerably slower than the descent velocity of individual blocks. Infrasound rockfall signal character is readily distinguishable from explosion infrasound, which is manifested by a relatively fixed location source with lower frequency content. In contrast, the rockfalls of Santiaguito possess higher frequencies dominated by 7.5 to 20 Hz energy. During our observation periods typical rockfall signals occurred ~10 times per hour and lasted tens of seconds or more. Array beamforming permitted detection of rockfall transients with amplitudes of only a few tens of millipascals that would be impossible to distinguish from noise using a single sensor. Conjoint time-synchronized video is used to corroborate location and to characterize various gravity-driven events.

  2. Station characteristics of the Singapore Infrasound Array

    NASA Astrophysics Data System (ADS)

    Perttu, Anna; Taisne, Benoit; Caudron, Corentin; Garces, Milton; Avila Encillo, Jeffrey; Ildefonso, Sorvigenaleon

    2016-04-01

    Singapore, located in Southeast Asia, presents an ideal location for an additional regional infrasound array, with diverse persistent natural and anthropogenic regional infrasound sources, including ~750 active or potentially active volcanoes within 4,000 kilometers. Previous studies have focused on theoretical and calculated regional signal detection capability improvement with the addition of a Singapore array. The Earth Observatory of Singapore installed a five element infrasound array in northcentral Singapore in late 2014, and this station began consistent real-time data transmission mid-2015. The Singapore array uses MB2005s microbarometers and Nanometrics Taurus digitizers. Automated array processing is carried out with the INFrasonic EneRgy Nth Octave (INFERNO) energy estimation suite, and PMCC (Progressive MultiChannel Correlation). The addition of the Singapore infrasound array to the existing International Monitoring System (IMS) infrasound stations in the region has increased regional infrasound detection capability, which is illustrated with the preliminary work on three observed meteor events of various sizes in late 2015. A meteor observed in Bangkok, Thailand in early September, 2015 was picked up by the CTBTO, however, another meteor observed in Bangkok in November was only recorded on the Singapore array. Additionally, another meteor observed over Sumatra was only recorded by one IMS station and the Singapore array. This study uses array processing and Power Spectral Density results for both the Singapore and publicly available regional IMS stations to examine station characteristics and detection capability of the Singapore array in the context of the regional IMS network.

  3. Improved Bayesian Infrasonic Source Localization for regional infrasound

    SciTech Connect

    Blom, Philip S.; Marcillo, Omar; Arrowsmith, Stephen J.

    2015-10-20

    The Bayesian Infrasonic Source Localization (BISL) methodology is examined and simplified providing a generalized method of estimating the source location and time for an infrasonic event and the mathematical framework is used therein. The likelihood function describing an infrasonic detection used in BISL has been redefined to include the von Mises distribution developed in directional statistics and propagation-based, physically derived celerity-range and azimuth deviation models. Frameworks for constructing propagation-based celerity-range and azimuth deviation statistics are presented to demonstrate how stochastic propagation modelling methods can be used to improve the precision and accuracy of the posterior probability density function describing the source localization. Infrasonic signals recorded at a number of arrays in the western United States produced by rocket motor detonations at the Utah Test and Training Range are used to demonstrate the application of the new mathematical framework and to quantify the improvement obtained by using the stochastic propagation modelling methods. Moreover, using propagation-based priors, the spatial and temporal confidence bounds of the source decreased by more than 40 per cent in all cases and by as much as 80 per cent in one case. Further, the accuracy of the estimates remained high, keeping the ground truth within the 99 per cent confidence bounds for all cases.

  4. Improved Bayesian Infrasonic Source Localization for regional infrasound

    DOE PAGES

    Blom, Philip S.; Marcillo, Omar; Arrowsmith, Stephen J.

    2015-10-20

    The Bayesian Infrasonic Source Localization (BISL) methodology is examined and simplified providing a generalized method of estimating the source location and time for an infrasonic event and the mathematical framework is used therein. The likelihood function describing an infrasonic detection used in BISL has been redefined to include the von Mises distribution developed in directional statistics and propagation-based, physically derived celerity-range and azimuth deviation models. Frameworks for constructing propagation-based celerity-range and azimuth deviation statistics are presented to demonstrate how stochastic propagation modelling methods can be used to improve the precision and accuracy of the posterior probability density function describing themore » source localization. Infrasonic signals recorded at a number of arrays in the western United States produced by rocket motor detonations at the Utah Test and Training Range are used to demonstrate the application of the new mathematical framework and to quantify the improvement obtained by using the stochastic propagation modelling methods. Moreover, using propagation-based priors, the spatial and temporal confidence bounds of the source decreased by more than 40 per cent in all cases and by as much as 80 per cent in one case. Further, the accuracy of the estimates remained high, keeping the ground truth within the 99 per cent confidence bounds for all cases.« less

  5. IDC Infrasound technology development

    NASA Astrophysics Data System (ADS)

    Mialle, P.; Brown, D. J.; Le Bras, R.; Charbit, M. J. C.; Given, J. W.

    2014-12-01

    The first atmospheric event built only from infrasound arrivals was reported in the Reviewed Event Bulletin (REB) of the International Data Centre (IDC) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) in 2003. In the last decade, 48 infrasound stations from the International Monitoring System (IMS) have been installed and are transmitting data to the IDC. The infrasound component of the IMS daily registers infragenic signals originating from various sources such as volcanic eruptions, earthquakes, microbaroms, meteorites entering the atmosphere and accidental explosions. The IDC routinely and automatically processes infrasound data reviewed by interactive analysis; the detected and located events are then included in the IDC products. The IDC advances its methods and continuously improves its automatic system for the infrasound technology. The IDC focuses on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold by identifying ways to refine signal characterization methodology and association criteria. An objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the automatic bulletins when generating the reviewed event bulletins. A number of ongoing projects at the IDC will be presented, such as: - improving the detection accuracy at the station processing stage by enhancing the infrasound signal detector DFX-PMCC (Detection and Feature eXtraction - Progressive Multi-Channel Correlation) and by evaluating the performances of detection software. - separating infrasound data from other waveform technologies at the automatic network processing stage for technology development and for preparing the implementation of next generation of waveform association algorithm. Infrasound rules in Global Association (GA) are revisited to pursue a lower ratio of false alarms. - determining station noise for IMS infrasound, seismic and

  6. Using physics-based priors in a Bayesian algorithm to enhance infrasound source location

    NASA Astrophysics Data System (ADS)

    Marcillo, Omar; Arrowsmith, Stephen; Whitaker, Rod; Anderson, Dale; Nippress, Alexandra; Green, David N.; Drob, Douglas

    2014-01-01

    We show improvements in the precision of the Bayesian infrasound source localization (BISL) method by incorporating semi-empirical model-based prior information. Given a set of backazimuths and delay times at ≥2 arrays, BISL scans a parameter space (that comprises the horizontal coordinates, celerity and origin time) for the most likely solution. A key element of BISL is its flexibility; the method allows the incorporation of prior information to constrain the parameters. Our research focuses on generating model-based propagation catalogues using a comprehensive set of atmospheric scenarios, extracting celerity distributions based on range and azimuth from the catalogues and using these distributions as prior probability density functions to enhance the location solution from BISL. To illustrate the improvements in source location precision, we compare the BISL results computed using uniform celerity distribution priors with those using enhanced priors; as applied to: (1) a set of events recorded across a regional network and (2) a large accidental chemical explosion recorded by six infrasound arrays in Eurasia. Finally, we discuss efforts to improve the numerical implementation of BISL by expanding the parameter space to cover a richer set of parameters that can include station-specific celerity distributions.

  7. Optical observations of meteors generating infrasound: Weak shock theory and validation

    NASA Astrophysics Data System (ADS)

    Silber, Elizabeth A.; Brown, Peter G.; Krzeminski, Zbigniew

    2015-03-01

    We have recorded a data set of 24 cm sized meteoroids detected simultaneously by video and infrasound to critically examine the ReVelle (1974) weak shock meteor infrasound model. We find that the effect of gravity wave perturbations to the wind field and updated absorption coefficients in the linear regime on the initial value of the blast radius (R0), which is the strongly nonlinear zone of shock propagation near the body and corresponds to energy deposition per path length, is relatively small (<10%). Using optical photometry for ground truth for energy deposition, we find that the ReVelle model accurately predicts blast radii from infrasound periods (τ) but systematically underpredicts R0 using pressure amplitude. If the weak shock to linear propagation distortion distance is adjusted as part of the modeling process, we are able to self-consistently fit a single blast radius value for amplitude and period. In this case, the distortion distance is always much less (usually just a few percent) than the value of 10% assumed in the ReVelle model. Our study shows that fragmentation is an important process even for centimeter-sized meteoroids, implying that R0, while a good measure of energy deposition by the meteoroid, is not a reliable means of obtaining the meteoroid mass. We derived an empirical period-blast radius relation of the form R0 = 15.4τ - 0.5 (τ ≤ 0.7 s) and R0 = 29.1τ - 11.6 (τ > 0.7 s) appropriate to centimeter-sized meteoroids. Our observations suggest that meteors having blast radii as small as 1 m are detectable infrasonically at the ground, an order of magnitude smaller than previously considered.

  8. Implications from Meteoric and Volcanic Infrasound Measured in the Netherlands

    NASA Astrophysics Data System (ADS)

    Evers, L.

    2003-12-01

    Infrasound observations started in the Netherlands in 1986. Since then, several array configurations and instruments have been developed, tested and made operational. Currently, three infrasound arrays are continuously measuring infrasound with in-house developed microbarometers. The array apertures vary from 30 to 1500 meters and the number of instruments from 6 to 16 microbarometers. The inter-array distance ranges from 50 up to 150 km. This dense network of infrasound arrays is used to distinguish between earthquakes and sources in the atmosphere. Sonic booms, for example, can be experienced in the same manner as small (gas induced) earthquakes. Furthermore, Comprehensive Nuclear-Test-Ban Treaty (CTBT) related research is done. Meteors are one of the few natural impulsive sources generating energy in kT TNT equivalent range. Therefore, the study of meteors is essential to the CTBT where infrasound is applied as monitoring technique. Studies of meteors in the Netherlands have shown the capability of infrasound to trace a meteor through the stratosphere. The propagation of infrasound is in first order dependent on the wind and temperature structure of the atmosphere. The meteor's path could be reconstructed by using ECMWF atmospheric models for wind and temperature. The results were compared to visual observations, confirming the location, direction and reported origin time. The accuracy of the localization mainly depends on the applied atmospheric model and array resolution. Successfully applying infrasound depends on the array configuration that should be based on the -frequency depend- spatial coherence of the signals of interest. The array aperture and inter-element distance will play a decisive role in detecting low signal-to-noise ratios. This is shown by results from studies on volcanic infrasound from Mt. Etna (Italy) detected in the Netherlands. Sub-array processing on the 16 element array revealed an increased detectability of infrasound for small

  9. Infrasound characterization of some Yellowstone geysers' eruptions

    NASA Astrophysics Data System (ADS)

    Quezada-Reyes, A.; Johnson, J.

    2012-12-01

    Geysers are springs that intermittently erupt hot water and steam. As with volcanoes, infrasonic airwaves produced by different geysers provide information about the processes that occur near the nozzle, such as the amount of fluid released during eruptive episodes. The aim of this study was to investigate acoustic sources from different geyser behaviors observed at Lone Star, Sawmill and Great Fountain geysers, Yellowstone National Park, Wyoming. Acoustic signal were measured by arrays of microphones deployed around Lone Star and Great Fountain geysers between August 9th to 14th, 2011, and during one hour on August 16th, 2011 at Sawmill Geyser. Infrasound was analyzed with coincident video recordings to quantify and compare the pressure fields generated during explosive phases at the three geysers. We propose that the periodic infrasound recorded at Sawmill, and dominated by energy at 1 to 40 Hz, is generated by: 1) steam-filled bubble oscillations, and 2) subsequent bursting at the free surface resulting in a violent steam and water discharge. At Lone Star geyser, where ~18 m/s eruption jets endure for about 30 minutes, sound is dominated by higher frequency infrasound and audio-band signal evolving from 20 - 60 Hz to 40 - 85 Hz. We suggest that the infrasound tremor amplitudes are related to the transition of the erupted two-phase mixture from mostly water (low acoustic radiation) to steam (high acoustic radiation). At Great Fountain we observed three explosive bursts of water and steam during the last stage on the August 11 eruption with bi-modal infrasound pulses of up to 0.7 Pa-m. We model these pulses as volumetric sound sources and infer up to 32 m3 of fluid ejection. The variety of recordings reflect the variety of eruption mechanisms at the different geyser systems. Better understanding of the mechanisms of geyser infrasound radiation may help us to understand infrasound analogues at erupting silicic volcanoes, which are considerably more difficult to

  10. Infrasound detection of meteors

    NASA Astrophysics Data System (ADS)

    ElGabry, M. N.; Korrat, I. M.; Hussein, H. M.; Hamama, I. H.

    2017-06-01

    Meteorites that penetrate the atmosphere generate infrasound waves of very low frequency content. These waves can be detected even at large distances. In this study, we analyzed the infrasound waves produced by three meteors. The October 7, 2008 TC3 meteor fell over the north Sudan Nubian Desert, the February 15, 2013 Russian fireball, and the February 6, 2016 Atlantic meteor near to the Brazil coast. The signals of these three meteors were detected by the infrasound sensors of the International Monitoring System (IMS) of the Comprehensive Test Ban Treaty Organization (CTBTO). The progressive Multi Channel Technique is applied to the signals in order to locate these infrasound sources. Correlation of the recorded signals in the collocated elements of each array enables to calculate the delays at the different array element relative to a reference one as a way to estimate the azimuth and velocity of the coming infrasound signals. The meteorite infrasound signals show a sudden change in pressure with azimuth due to its track variation at different heights in the atmosphere. Due to movement of the source, a change in azimuth with time occurs. Our deduced locations correlate well with those obtained from the catalogues of the IDC of the CTBTO.

  11. Infrasound Monitoring of Natural Hazards

    NASA Astrophysics Data System (ADS)

    Arrowsmith, S.

    2015-12-01

    Infrasound is generated by a wide variety of energetic natural and anthropogenic phenomena that originate in the solid earth, ocean, and atmosphere. Because the absorption of infrasound is low, it can propagate long distances through atmospheric waveguides, making it a valuable tool for remote monitoring of hazards. Advances in using infrasound for monitoring energetic events in the solid earth, oceans, and atmosphere are being driven by the wealth of new datasets in addition to advances in modeling source and propagation physics. This presentation provides an overview of recent advances in infrasound monitoring of natural hazards, focusing on selected hazards in the earth (earthquakes and volcanoes), ocean (tsunamis), and atmosphere (meteoroids).

  12. Infrasound signals from the underground nuclear explosions of North Korea

    NASA Astrophysics Data System (ADS)

    Che, Il-Young; Park, Junghyun; Kim, Inho; Kim, Tae Sung; Lee, Hee-Il

    2014-07-01

    We investigated the infrasound signals from seismic ground motions induced by North Korea's underground nuclear explosions, including the recent third explosion on 2013 February 12. For the third explosion, the epicentral infrasound signals were detected not only by three infrasound network stations (KSGAR, ULDAR and YAGAR) in South Korea but also by two nearby International Monitoring System infrasound stations, IS45 and IS30. The detectability of the signals was limited at stations located on the relatively east side of the epicentre, with large azimuth deviations due to very favourable atmospheric conditions for eastward propagation at stratospheric height in 2013. The stratospheric wind direction was the reverse of that when the second explosion was conducted in 2009 May. The source location of the epicentral infrasound with wave parameters determined at the multiple stations has an offset by about 16.6 km from the reference seismic location. It was possible to determine the infrasonic location with moderate accuracy by the correction of the azimuth deviation due to the eastward winds in the stratosphere. In addition to the epicentral infrasonic signals, diffracted infrasound signals were observed from the second underground nuclear explosion in 2009. The exceptional detectability of the diffracted infrasound was a consequence of the temporal formation of a thin atmospheric inversion layer over the ocean surface when the event occurred.

  13. Infrasound tremor from bubble burst eruptions in the viscous shallow crater lake of White Island, New Zealand, and its implications for interpreting volcanic source processes

    NASA Astrophysics Data System (ADS)

    Jolly, Arthur; Kennedy, Ben; Edwards, Matt; Jousset, Philippe; Scheu, Bettina

    2016-11-01

    White Island volcano, New Zealand, produced two periods (January-February and July 2013) of episodic and persistent eruptions through a viscous shallow mud/sulphur pool. The eruptions included an initial hemispherical bubble burst, which was intermittently followed by an up-channel gas jet, and finally a late stage heaving of a mud/sulphur/water suspension. The late stage heave was systematically directed south-eastward as far as 30-40 m from the vent. The associated infrasound time-series included harmonic tremor on permanent stations WIZ and WSRZ. Detailed inspection showed that the tremor was composed of numerous discrete double pulse events without a strong periodic event repetition. The first pulse had highly similar waveforms event-to-event and a notable distortion of the waveform period between the two infrasound stations located on opposites sides from the directed eruption source. The second pulse occurred about 1.5-2.5 s later and was weakly observed on station WSRZ. Where the video can be rigorously linked to the double pulse infrasound signals we interpret aspects of the distinctive eruptive regimes. For this case, the regime dynamics are driven by the propagation of numerous discrete gas slugs though the shallow viscous muddy crater lake, each generating a distinct bubble burst with subsequent eruption heave and associated double pulse infrasound events. The double pulse events are the source of the persistent harmonic tremor having fundamental and overtone spectral frequencies but are not interpreted as related to cavity resonance or a repetitious comb function. Instead the activity is produced by a single event producing a specific two pulse source time function. The observed distortion in the first pulse wave period at WIZ and WSRZ may be ascribed to a Doppler shift associated with the directivity observed in the initial jet/heave eruption process. We surmise that double pulse source dynamics and directivity effects may be generically extended to

  14. Constraining the Spatial and Temporal Variability of Atmospheric Conditions to Explore the Infrasound Detection of Volcanic Eruptions in Alaska

    NASA Astrophysics Data System (ADS)

    Iezzi, A. M.; Schwaiger, H. F.; Fee, D.; Haney, M. M.

    2015-12-01

    Alaska's over 50 historically active volcanoes span 2,500 kilometers, and their eruptions pose great threats to the aviation industry. This makes both prompt observations of explosion onsets and changes in intensity a necessity. Due to their expansive range and remoteness, these volcanoes are predominantly monitored by local seismic networks, remote observations including satellite imagery and infrasound sensors. Infrasound is an especially crucial tool in this area because infrasound data collection is not obstructed by frequent cloud cover (as in satellite imagery) and infrasound waves can travel hundreds to thousands of kilometers. However, infrasound station coverage is relatively sparse and strong wind and temperature gradients in the atmosphere create multiple waveguides and shadow zones where the propagation of infrasound is enhanced and diminished, respectively. To accurately constrain volcanic source information and the long-range propagation of infrasound waves, a detailed characterization of the spatial and temporal variability of the atmosphere is vital. These properties can be constrained using a ground-to-space model similar to that of Drob et al. (2003) based upon varied meteorological observations and applied to infrasound waves to model the propagation of infrasound. Here we present the first results of a re-analysis system constructed by the Alaska Volcano Observatory to accurately characterize and model long-range infrasound propagation from volcanic eruptions. We select a number of case studies to examine infrasound detections (or lack thereof) from recent eruptions of Alaskan volcanoes, including the November 2014 eruption of Pavlof Volcano and July 2015 eruption of Cleveland Volcano. Detailed examination of the acoustic propagation conditions will provide additional insight into detection capability and eruption dynamics with future work aiming to implement real-time long-range infrasound propagation modeling.Drob, Douglas P., J. M. Picone

  15. Infrasound studies and seismic station development

    NASA Astrophysics Data System (ADS)

    Golden, Paul W.

    A large-scale set of experiments involving measurement of infrasound (long period acoustic signals) from high altitude explosions on rockets launched at White Sands Missile Range (WSMR) was conducted during 2005 and 2006. Studies of the infrasound signals from the explosions determined that propagation patterns were predictable from climatology data but that the predictions of explosive yield using established period/yield relationships underestimated known yields by about one order of magnitude. In addition, yield estimates did not scale at source heights greater than about 40 km indicating some physical change in the atmosphere above these heights that was not included in the scaling relations. A subsequent study to the WSMR experiments motivated by the apparent discrepancies in yield estimation and studies of infrasound propagation to distances less than about 250 km was completed. This distance range is traditionally known as the zone of silence where it was believed that no energy would return to the ground surface based on classical ray theory using average atmospheric models. This study supports similar observations by others that documents the presence of signals at these distances and relates them to empirically determined atmospheric models which predict complex and multiple energy returns to the surface. In addition to quantification of these propagation path effects the explosive source strength is calibrated using a period-yield scaling relationship originally developed for nuclear explosions on the surface. Significant work conducted by the Geophysics Laboratory at Southern Methodist University since about 1993 focusing on the design, construction, installation and utilization of high performance seismic and infrasound regional arrays is documented. These designs have made significant international contributions to the field of regional seismic and infrasound monitoring for purposes of characterizing man made activities and in particular, the

  16. Results from a student built balloon-borne infrasound sensing instrument

    NASA Astrophysics Data System (ADS)

    Klein, Viliam; Young, Eliot; Bowman, Daniel; Abernathy, Robert

    2017-04-01

    Balloon-borne infrasound sensors should have two advantages over ground based counterparts: lack of wind noise, and the potential for infrasound concentration in stratospheric ducts. In this paper we present the design and results from a student-built payload for sensing infrasound waves (between 0.1Hz to 20Hz) from a NASA stratospheric balloon that reached altitudes of 37km on September 28th of 2016. The SISE (Student Infrasound Experiment) uses a unique arrangement of COTS differential pressure sensors and student designed signal conditioning to eliminate noise and sense infrasound waves below 20Hz. To calibrate the sensitivity of ground based and balloon-borne sensors, we contracted EMRTC to set off three large explosions from Socorro NM during flight, roughly 200-400 km west of the balloon position at the time of the explosions. The goal of this experiment was to detect the artificially generated infrasound waves at altitude despite the lower expected amplitudes. This presentation contains discussions of the overall design for the instrument, laboratory and in flight performance characteristics, as well as in flight observations of infrasound generated from the artificial sources. The instrument successfully detected infrasound waves of about 0.03 Pa at an altitude of 37 kilometers and a distance of 350km from the source.

  17. Infrasound as upper atmospheric monitor

    NASA Astrophysics Data System (ADS)

    Assink, Jelle D.

    Understanding and specification of the higher altitudes of the atmosphere with global coverage over all local times is hampered by the challenges of obtaining direct measurements in the upper atmosphere. Methods to measure the properties of the atmosphere above the stratopause is an active area of scientific research. In this thesis, we revisit the use of infrasound as a passive remote sensing technique for the upper atmosphere. Signals from the Tungurahua volcano in Ecuador are used to investigate the behavior of the upper atmosphere. Depending on the atmospheric conditions, stratospheric, mesospheric and thermospheric arrivals are observed during intervals of explosive volcanic activity. It is found that the travel times and dominant frequencies of the thermospheric arrivals exhibit a coherent variability with periods equal to those of the tidal harmonics. Theoretical predictions using atmospheric specifications show that the stratospheric arrivals are predicted within 1% of the observed value. For thermospheric arrivals, this error can be as high as 10%. The error in thermospheric celerities is found to be in accord with the typical uncertainty in upper atmospheric winds. Given the observed response of the infrasound celerities to upper atmospheric tidal variability, it is suggested that infrasound observations may be used as an additional source of information to constrain the atmospheric specifications in the upper atmosphere. We present corrected wind profiles that have been obtained by minimizing misfits in traveltime and source location using a Bayesian statistics grid search algorithm. Also, a Levenberg-Marquardt search algorithm is developed. Additionally, a new numerical method has been developed to solve the problem of infrasound propagation in a stratified medium with (high Mach number) background flow, based on a modal expansion. The underlying mathematics is by no means new and has been earlier described. This solution goes beyond the effective sound

  18. Refinement of bolide characteristics from infrasound measurements

    NASA Astrophysics Data System (ADS)

    Gi, Nayeob; Brown, Peter

    2017-09-01

    We have detected and performed signal measurements on 78 individual bolide events as recorded at 179 infrasound stations between 2006 and 2015. We compared period-yield relations with AFTAC nuclear period-yield data, finding these to be similar with a slight offset. Scatter in period measurements for individual bolide is found to be caused in part by station noise levels and by attenuation effects with range. No correlation was found between the infrasound signal period and any of bolide height at peak brightness, entry speed or impact angle. We examined in detail three well constrained bolides having energy deposition curves, known trajectories and infrasound detections finding some evidence at shorter ranges that a component of station period scatter is due to varying source heights sampled by different stations. However, for longer-range stations in these three case studies, we were not able to assign unique source heights using raytracing due to large uncertainties in atmospheric conditions. Our results suggest that while source height contributes to the observed variance in infrasound signal periods from a given bolide, range and station noise play a larger role.

  19. Characteristic Surface Processes Between Atmosphere, Cryosphere and Oceanic Environment Inferred from Infrasound Array Observations in Lützow-Holm Bay, East Antarctica

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Kanao, M.; Yamamoto, M. Y.; Kakinami, Y.; Murayama, T.; Okada, K.; Toda, S.; Matsushima, T.

    2014-12-01

    Infrasound is sub-audible sound whose frequency range is about 3 mHz to 20 Hz. Because this frequency is common between atmospheric, oceanic and solid earth vibrations, those waves are interacting with each other and interaction itself generates infrasound. At polar region, cryosphere also play an important role for generation and propagation of infrasound. The Japanese Antarctic infrasound observation started at April 2008. A sensor was installed at Syowa Station (SYO) in Lützow-Holm Bay (LHB) of East Antarctica, as a part of the International Polar Year. Characteristic infrasound waves observed at SYO demonstrate physical interaction involving environmental changes in the Antarctic region. Continuous recordings of infrasound clearly indicate existence of the hums generated by ocean-atmosphere interaction (microbaroms) with peaks of 0.1 to 0.25 Hz. Because larger amount of sea-ice extending around the LHB near SYO suppress ocean wave, the microbaroms become weak during austral winter. Following success of pilot observation, in austral summer in 2013, we extended one-sensor observation at SYO to 3-sensor arrayed observations, and installed a few field stations along the coast of the LHB. Newly established SYO array clearly detected the propagating directions and frequency contents of the microbaroms from Southern Ocean. In addition, we found harmonic signals around lowermost human audible band, however, currently unclear how and what generating hamonic signals. Those signals are recorded under windy condition. Since our system has no mechanical resonance at those frequency ranges, we speculate that the characteristic harmonic signals are probably related to local surficial phenomena such as ice sheet vibration generated by katabatic winds. Infrasound measurement at Antarctica could be a new proxy for monitoring a regional environmental change in high southern latitude. In such point of view, we will continue and improve the observations at and around SYO

  20. Assessment of Infrasound Detection Capabilities in the Western US Using a Combination of Infrasound Arrays and Single Seismometers

    NASA Astrophysics Data System (ADS)

    Park, J.; Hayward, C.; Stump, B. W.

    2016-12-01

    Ground truth sources can be useful for documenting how infrasound observations are affected by atmospheric conditions as well as testing predictive capabilities of the atmospheric model. To assess these issues, we focus on the infrasound analysis using a hybrid of regional scale seismic stations and infrasound arrays in the western US. The station distributions vary in time when USArray Transportable Array (TA) and local seismic network were installed. A total of 56 ground truth events were collected from static rocket motor burn tests (long duration up to 3 minutes) and rocket body demolitions (impulsive signals) in Utah from 2003 to 2013. In order to review hundreds of stations for individual events, automated infrasound detection and association techniques were developed. The detection procedure is based on STA/LTA trigger in combinations with spectral and amplitude analyses. Detected signals were subsequently associated using the closest three stations with estimates of phase velocity and azimuth used to refine the detections. The automatic detections indicate that infrasound signals from both types of sources are observed to distances of 600 km with some observed beyond 700 km. Infrasound arrival predictions using ground-to-space (G2S) atmospheric specifications compare well with both automatic and analysts infrasound picks including celerity and amplitude documenting seasonal variations in atmospheric conditions. The average detection percentages are 28.8 % and 24.7 % for rocket demolition and burn test datasets, respectively, twice as high as those produced by the analyst. Additional work is needed to quantify the effects of station distribution, atmospheric conditions, source coupling, acoustic to seismic coupling at seismometers, local noise levels and effectiveness of network processing on the proposed automated procedures.

  1. An operational approach for infrasound multi-array processing

    NASA Astrophysics Data System (ADS)

    Vergoz, J.; Le Pichon, A.; Herry, P.; Blanc, E.

    2009-04-01

    The infrasound network of the International Monitoring Network (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is currently not fully established. However, it has demonstrated its capability for detecting and locating infrasonic sources like meteorites as well as volcanic eruptions on a global scale. Unfortunately, such ground truth events are rare. Therefore, regions with dense infrasound networks have to be considered in order to test and calibrate detection and location procedures (Le Pichon. et al. 2008, J. Geophys. Res., 113, D12115, doi:10.1029/2007JD009509). In Central Europe, several years of continuous infrasound recordings are available for many infrasound arrays, where not all of them are part of the IMS. Infrasound waveforms are routinely processed in the 0.1 to 4 Hz frequency band using PMCC as a real-time detector. After applying a categorization procedure to remove detections associated with environmental noise, a blind fusion provides a list of events to be reviewed by the analyst. In order to check the geophysical consistency of the located events, an interactive tool has been developed. All results of the automatic processing are presented along with a realistic estimate of the network detection capability which incorporates near-real time atmospheric updates. Among the dominant acoustic sources of human origin, peaks in the geographical distribution of infrasound events correspond well with seismically active regions where operational mines have been identified. With the increasing number of IMS and regional cluster infrasound arrays deployed around the globe, conducting consistent analyses on a routine-basis provides an extensive database for discriminating between natural and artificial acoustic sources. Continuing such studies may also help quantifying relationships between infrasonic observables and atmospheric specification problems, thus opening new fields for investigations into inverse problems.

  2. Infrasound Studies at the USArray (Invited)

    NASA Astrophysics Data System (ADS)

    de Groot-Hedlin, C. D.

    2013-12-01

    Many surface and atmospheric sources, both natural and anthropogenic, have generated infrasound signals that have been recorded on USArray transportable array (TA) seismometers at ranges up to thousands of kilometers. Such sources, including surface explosions, large bolides, mining events, and a space shuttle, have contributed to an understanding of infrasound propagation. We show examples of several atmospheric sources recorded at the TA. We first used USArray data to investigate infrasound signals from the space shuttle 'Atlantis'. Inclement weather in Florida forced the shuttle to land at Edwards Air Force Base in southern California on June 22, 2007, passing near three infrasound stations and several hundred seismic stations in northern Mexico, southern California, and Nevada. The high signal-to-noise ratio, broad receiver coverage, and Atlantis' positional information allowed us to test infrasound propagation modeling capabilities through the atmosphere to hundreds of kilometers range from the shuttle's path. Shadow zones and arrival times were predicted by tracing rays launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model. Both models predict alternating regions of high and low ensonification to the NW, in line with observations. However, infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification, possibly due to uncertainties in stratospheric wind speeds. The models also predict increasing waveform complexity with increasing distance, in line with observations. Several hundreds of broadband seismic stations in the U.S. Pacific Northwest recorded acoustic to seismic coupled signals from a large meteor that entered the atmosphere above northeastern Oregon on 19 February 2008. The travel times of the first arriving energy are consistent with a terminal explosion source model, suggesting that the large size of the explosion

  3. Three-Dimensional, Finite-Difference, Time-Domain Modeling of Local Volcano Infrasound Radiation Using GPU

    NASA Astrophysics Data System (ADS)

    Kim, K.; Lees, J. M.

    2013-12-01

    Since volcano infrasound is a direct measure of atmospheric pressure fluctuation near open-vent activity, it can provide important constraints on eruption source parameters including the volume of gas released and eruption velocity. Local infrasound data (<15 Km) have been used to quantify and characterize acoustic sources of volcanic eruptions since they are relatively less affected by atmospheric velocity structures in the near field. The interaction of volcano infrasound sources and complex topography near the volcanic edifice, however, has not been fully explored. Infrasound observations from world-wide volcanoes and two-dimensional numerical modeling of infrasound radiation in the vicinity of the crater suggest a strong distortion of the wavefield by local topography [Kim and Lees, GRL, 2011]. To get a complete picture of these effects, however, full three-dimensional modeling is required. We have developed a new, accelerated, 3D finite-difference time-domain program using GPU (Grpahic Processing Units) to simulate local infrasound propagation near volcanoes, while taking into account complex topography, local wind distortion, and atmospheric sound velocity structures. While CPU-based 3D FDTD method requires a prohibitive amount of computational resources, GPU-based algorithms significantly reduce the computational time of infrasound modeling, making parallel processing practical even on a desktop computer. In these simulations we provide a comprehensive solution of volcano infrasound radiation assuming different acoustic sources and real volcano topography. We illustrate the interaction of local vent topography and difference acoustic sources and how they combine to affect the infrasound wavefield. By removing topographic effects from local infrasound observation we can begin to quantitatively model acoustic sources and finally establish the partitioning of energy, at the vent, between the acoustic and seismic wavefields.

  4. Study of IDC infrasound REB solutions using Egyptian National Seismic Network data

    NASA Astrophysics Data System (ADS)

    Ali, Sherif M.; Polich, Paul

    2015-04-01

    Infrasound is one of three waveform technologies which are part of the Comprehensive Nuclear Test Ban Treaty (CTBT) verification regime. The International Monitoring System (IMS) of the CTBT consists of 337 monitoring stations and laboratories world-wide. These facilities include 45 infrasound stations, installed world-wide and transmitting data to the International Data Centre (IDC). Since early 2010, the IDC began routine automatic and interactive processing of infrasound data; the detected and located events are systematically included in the Reviewed Event Bulletin (REB). Infrasound events are frequently characterized by a small number of infrasound phase associations. This poses a challenge to obtaining high-confidence event solutions during routine processing of infrasound data. This study focuses on six infragenic events from the REB, occurring between January 2011 and December 2014, which were thoroughly analyzed at the IDC. The selected events were characteristically seismo-acoustic, and corroborated by seismic recordings of the Egyptian National Seismic Network (ENSN) operated by the National Research Institute of Astronomy and Geophysics (NRIAG). Utilizing this additional local network data of ENSN enables sharper assessment of the IDC published event solutions. Notably, the events were recorded within Egypt and regional surroundings where infrasound waves were generated. The events were detected by IMS infrasound stations located up to 7000 kilometers away. Additional analyses, beyond the six infragenic events from the REB, will also consider some valid infragenic events that fall short of stringent REB Event Definition Criteria. The events will primarily consist of two defining stations with lower-confidence event solutions. The selected events, when confirmed by the seismic observations at ENSN, provide a unique dataset for evaluating IDC infrasound event solutions. Further objectives of the study seek to measure the performance of the IMS network for

  5. Long-range infrasound monitoring of eruptive volcanoes.

    NASA Astrophysics Data System (ADS)

    Marchetti, Emanuele; Innocenti, Lorenzo; Ulivieri, Giacomo; Lacanna, Giorgio; Ripepe, Maurizio

    2016-04-01

    The efficient long-range propagation in the atmosphere makes infrasound of active volcanoes extremely promising and opens new perspectives for volcano monitoring at large scale. In favourable propagation conditions, long-range infrasound observations can be used to track the occurrence and the duration of volcanic eruptions also at remote non-monitored volcanoes, but its potential to infer volcanic eruptive source term is still debated. We present results of comparing five years of infrasound of eruptive activity at Mt.Etna volcano (Italy) recorded both at local (~5 km) and at regional distances (~600 km) from the source. Infrasound of lava fountains at Etna volcano, occurring in between 2010 and 2015, are analysed in terms of the local and regional wavefield record, and by comparing to all available volcanic source terms (i.e. plume height and mass eruption rates). Besides, the potential of near real-time notification of ongoing volcanic activity at Etna volcano at a regional scale is investigated. In particular we show how long range infrasound, in the case of Etna volcano, can be used to promptly deliver eruption notification and reliability is constrained by the results of the local array. This work is performed in the framework of the H2020 ARISE2 project funded by the EU in the period 2015-2018.

  6. Characterization of volcanic activity using observations of infrasound, volcanic emissions, and thermal imagery at Karymsky Volcano, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Lopez, T.; Fee, D.; Prata, F.

    2012-04-01

    Karymsky Volcano is one of the most active and dynamic volcanoes in Kamchatka, with activity ranging from vigorous degassing, frequent ash emissions, and apparent vent sealing, all punctuated by daily to weekly explosive magmatic eruptions. Recent studies have highlighted the strengths in using complementary infrasound measurements and remote volcanic emission measurements to characterize volcanic activity, with the potential to discriminate emission-type, approximate ash-cloud height, and estimate SO2 emission mass. Here we use coincident measurements of infrasound, SO2, ash, and thermal radiation collected over a ten day period at Karymsky Volcano in August 2011 to characterize the observed activity and elucidate vent processes. The ultimate goal of this project is to enable different types of volcanic activity to be identified using only infrasound data, which would significantly improve our ability to continuously monitor remote volcanoes. Four types of activity were observed. Type 1 activity is characterized by discrete ash emissions occurring every 1 - 5 minutes that either jet or roil out of the vent, by plumes from 500 - 1500 m (above vent) altitudes, and by impulsive infrasonic onsets. Type 2 activity is characterized by periodic pulses of gas emission, little or no ash, low altitude (100 - 200 m) plumes, and strong audible jetting or roaring. Type 3 activity is characterized by sustained emissions of ash and gas, with multiple pulses lasting from ~1 - 3 minutes, and by plumes from 300 - 1500 m. Type 4 activity is characterized by periods of relatively long duration (~30 minutes to >1 hour) quiescence, no visible plume and weak SO2 emissions at or near the detection limit, followed by an explosive, magmatic eruption, producing ash-rich plumes to >2000 m, and centimeter to meter (or greater) sized pyroclastic bombs that roll down the flanks of the edifice. Eruption onset is accompanied by high-amplitude infrasound and occasionally visible shock

  7. Use of the IMS infrasound network for global atmospheric studies

    NASA Astrophysics Data System (ADS)

    Blanc, Elisabeth; Le Pichon, Alexis; Ceranna, Lars; Farges, Thomas

    2010-05-01

    The development of the Infrasound International Monitoring System (IMS), used for the verification of the Comprehensive Test Ban Treaty, represents a powerful tool to measure permanently, at a global scale and over large periods of time, the disturbances of the atmosphere. The network is mostly sensitive to infrasound in the range 0.02 to 5 Hz, but it also measures gravity waves at lower frequencies and tidal waves. Measurements with the IMS infrasound network provide both the state of the atmospheric wave guide and of the atmospheric waves which can be used to study the dynamics of the atmosphere. The first way is to study the variability of infrasound from quasi continuous sources such as ocean swells or volcanoes in relation with changes in large scale atmospheric structures. Since infrasound propagate in the stratosphere and mesosphere, atmospheric parameters which affect the infrasound propagation can be investigated from ground measurements of infrasound. Azimuth changes of infrasound from volcanis eruption were used to retrieve mesospheric zonal winds. The amplitude fluctuations of infrasound from ocean swells represent planetary waves which modulate the atmospheric wave guide. Fluctuations are much larger in Northern hemispheres than in Southern hemisphere, because the amplitude of planetary waves is larger in Northern hemisphere where continental areas are more important. Infrasound monitoring also revealed anomalies at a seasonal scale in Antarctica or at the scale of several days in Arctic regionsin relation with Sudden Stratospheric Warming. The second way is the direct observation of large scale gravity waves. These waves, mainly produced in the troposphere, propagate upwards and break in the stratosphere producing a chaotic forcing of the stratosphere. This is at the origin of a slow and large scale motion in which air masses are driven upward and poleward from the tropical lower stratosphere. In polar regions, they are pushed downward producing

  8. Recent progress in nuclear test detection using infrasound technology

    NASA Astrophysics Data System (ADS)

    Blanc, E.; LE Pichon, A.; Ceranna, L.; Brachet, N.

    2016-12-01

    The high performances of the International Monitoring System infrasound network were very well demonstrated by the detection and analysis of many Ground Truth Events in various environmental conditions. This presentation highlights recent progresses based on an improved description of both signal and atmosphere. Firstly, progress concerns observations and data analysis of big data sets. The infrasound sensors provide broadband signals in the interest frequency range. However, signals are generally analyzed in several parallel frequency bands. The currently used Progressive Multi-Channel Correlation algorithm (PMCC) is now evolving to process the useful information in a broad standardized frequency range, leading to a more accurate characterization of both source and noise which could benefit to operational monitoring purposes. Secondly, progress concerns the development of experimental infrasound stations which form a dense infrasound network, especially in Europe, enhancing the detectability of infrasound events. Thirdly, progress concerns an improved representation of the atmosphere. Systematic processing highlights the necessity to improve propagation modeling in the wave guide between ground and stratosphere-mesosphere-thermosphere system to interpret the observations. The predicted detection periods of volcano eruptions using near field observations and propagation models are shorter than the periods observed in the far field. The lack of representation in the models of large scale atmospheric disturbances such as gravity, planetary waves and sudden stratospheric warming events, is at the origin of these differences. New methods are developed to parameterize these disturbances for further assimilation in atmospheric models, as planned in the framework of the Atmospheric dynamics Research InfraStructure in Europe (ARISE) project. One application is the improvement of the detection capability simulations used for the evaluation of the performances of existing

  9. Infrasound signals coupled from an underwater explosion

    NASA Astrophysics Data System (ADS)

    Che, I.-Y.; Kim, T. S.; Lee, H.-I.

    2012-04-01

    On 26 March 2010, a South Korean warship, Cheoanham, was sunken down offshore of an island, Bakryeong, in the Yellow Sea, South Korea. In the island that is near to the incident site, were a seismo-acoustic array and a broadband seismic station in operation. These stations recorded clear seismic and infrasonic signals associated with the warship-sinking. In addition, five infrasound arrays being operated in the inland of South Korea also detected the infrasound signals propagated up to 348 km from the source. We studied the seismic and infrasonic signatures from the event for the determination of exact source location and explanation of coupling phenomena among three different media; sea, solid earth and atmosphere. For the accurate source localization we fused all the available seismo-acoustic information of arrival time and azimuth estimates of coupled seismic and infrasonic signals. The calculated location is nearly coincident with the event location reported by the Civilian Military Joint Investigation Group, which shows seismo-acoustic location is much better than those calculated with just seismic or infrasonic dataset. The relationship between explosion depth and charge was constrained with the period of the observed infrasonic signals. The attenuated amplitude of infrasound signal was corrected to estimate the perturbed air pressure at source location.

  10. Assessing and optimizing infrasound network performance: application to remote volcano monitoring

    NASA Astrophysics Data System (ADS)

    Tailpied, D.; LE Pichon, A.; Marchetti, E.; Kallel, M.; Ceranna, L.

    2014-12-01

    Infrasound is an efficient monitoring technique to remotely detect and characterize explosive sources such as volcanoes. Simulation methods incorporating realistic source and propagation effects have been developed to quantify the detection capability of any network. These methods can also be used to optimize the network configuration (number of stations, geographical location) in order to reduce the detection thresholds taking into account seasonal effects in infrasound propagation. Recent studies have shown that remote infrasound observations can provide useful information about the eruption chronology and the released acoustic energy. Comparisons with near-field recordings allow evaluating the potential of these observations to better constrain source parameters when other monitoring techniques (satellite, seismic, gas) are not available or cannot be made. Because of its regular activity, the well-instrumented Mount Etna is in Europe a unique natural repetitive source to test and optimize detection and simulation methods. The closest infrasound station part of the International Monitoring System is located in Tunisia (IS48). In summer, during the downwind season, it allows an unambiguous identification of signals associated with Etna eruptions. Under the European ARISE project (Atmospheric dynamics InfraStructure in Europe, FP7/2007-2013), experimental arrays have been installed in order to characterize infrasound propagation in different ranges of distance and direction. In addition, a small-aperture array, set up on the flank by the University of Firenze, has been operating since 2007. Such an experimental setting offers an opportunity to address the societal benefits that can be achieved through routine infrasound monitoring.

  11. Strombolian surface activity regimes at Yasur volcano, Vanuatu, as observed by Doppler radar, infrared camera and infrasound

    NASA Astrophysics Data System (ADS)

    Meier, K.; Hort, M.; Wassermann, J.; Garaebiti, E.

    2016-08-01

    In late 2008 we recorded a continuous multi-parameter data set including Doppler radar, infrared and infrasound data at Yasur volcano, Vanuatu. Our recordings cover a transition in explosive style from ash-rich to ash-free explosions followed again by a phase of high ash discharge. To assess the present paradigm of Strombolian behavior in this study we investigate the geophysical signature of these different explosive episodes and compare our results to observations at Stromboli volcano, Italy. To this end we characterize Yasur's surface activity in terms of material movement, temperature and excess pressure. The joint temporal trend in these data reveals smooth variations of surface activity and regime-like persistence of individual explosion forms over days. Analysis of all data types shows ash-free and ash-rich explosive styles similar to those found at Stromboli volcano. During ash-free activity low echo powers, high explosion velocities and high temperatures result from the movement of isolated hot ballistic clasts. In contrast, ash-rich episodes exhibit high echo powers, low explosion velocities and low temperatures linked to the presence of colder ash-rich plumes. Furthermore ash-free explosions cause high excess pressure signals exhibiting high frequencies opposed to low-amplitude, low-frequency signals accompanying ash-rich activity. To corroborate these findings we compare fifteen representative explosions of each explosive episode. Explosion onset velocities derived from Doppler radar and infrared camera data are in excellent agreement and consistent with overall observations in each regime. Examination of infrasound recordings likewise confirms our observations, although a weak coupling between explosion velocity and excess pressure indicates changes in wave propagation. The overall trend in explosion velocity and excess pressure however demonstrates a general correlation between explosive style and explosion intensity, and points to stability of the

  12. Infra-sound Signature of Lightning

    NASA Astrophysics Data System (ADS)

    Arechiga, R. O.; Badillo, E.; Johnson, J.; Edens, H. E.; Rison, W.; Thomas, R. J.

    2012-12-01

    We have analyzed thunder from over 200 lightning flashes to determine which part of thunder comes from the gas dynamic expansion of portions of the rapidly heated lightning channel and which from electrostatic field changes. Thunder signals were recorded by a ~1500 m network of 3 to 4 4-element microphone deployed in the Magdalena mountains of New Mexico in the summers of 2011 and 2012. The higher frequency infra-sound and audio-range portion of thunder is thought to come from the gas dynamic expansion, and the electrostatic mechanism gives rise to a signature infra-sound pulse peaked at a few Hz. More than 50 signature infra-sound pulses were observed in different portions of the thunder signal, with no preference towards the beginning or the end of the signal. Detection of the signature pulse occurs sometimes only for one array and sometimes for several arrays, which agrees with the theory that the pulse is highly directional (i.e., the recordings have to be in a specific position with respect to the cloud generating the pulse to be able to detect it). The detection of these pulses under quiet wind conditions by different acoustic arrays corroborates the electrostatic mechanism originally proposed by Wilson [1920], further studied by Dessler [1973] and Few [1985], observed by Bohannon [1983] and Balachandran [1979, 1983], and recently analyzed by Pasko [2009]. Pasko employed a model to explain the electrostatic-to-acoustic energy conversion and the initial compression waves in observed infrasonic pulses, which agrees with the observations we have made. We present thunder samples that exhibit signature infra-sound pulses at different times and acoustic source reconstruction to demonstrate the beaming effect.

  13. Infrasound from large surf

    NASA Astrophysics Data System (ADS)

    Garcés, M.; Aucan, J.; Fee, D.; Caron, P.; Merrifield, M.; Gibson, R.; Bhattacharyya, J.; Shah, S.

    2006-03-01

    Simultaneous infrasonic, visual, and ocean-bottom pressure sensor observations of large swells on the island of Kauai and small to medium-sized surf on the island of Hawaii yielded a clear relationship between breaking wave height and low-frequency atmospheric sound amplitudes in the 1-20 Hz frequency range. These experiments confirmed that infrasound can be generated by barreling waves as well as by waves crashing against rocky shorelines and exposed ledges. As will be demonstrated in a companion paper, breaking wave period may also be extracted from infrasound data. The results of these experiments demonstrate that low-frequency sound may be used for real-time estimates of the amplitude, period, and spatial distribution of surf in the littoral zone, with a potential application to the identification of breaking wave types.

  14. Frequency and Size of Strombolian Eruptions from the Phonolitic Lava Lake at Erebus Volcano, Antarctica: Insights from Infrasound and Seismic Observations on Bubble Formation and Ascent

    NASA Astrophysics Data System (ADS)

    Rotman, H. M. M.; Kyle, P. R.; Fee, D.; Curtis, A.

    2015-12-01

    Erebus, an active intraplate volcano on Ross Island, commonly produces bubble burst Strombolian explosions from a long-lived, convecting phonolitic lava lake. Persistent lava lakes are rare, and provide direct insights into their underlying magmatic system. Erebus phonolite is H2O-poor and contains ~30% anorthoclase megacrysts. At shallow depths lab measurements suggest the magma has viscosities of ~107 Pa s. This has implications for magma and bubble ascent rates through the conduit and into the lava lake. The bulk composition and matrix glass of Erebus ejecta has remained uniform for many thousands of years, but eruptive activity varies on decadal and shorter time scales. Over the last 15 years, increased activity took place in 2005-2007, and more recently in the 2013 austral summer. In the 2014 austral summer, new infrasound sensors were installed ~700 m from the summit crater hosting the lava lake. These sensors, supplemented by the Erebus network seismic stations, recorded >1000 eruptions between 1 January and 7 April 2015, with an average infrasound daily uptime of 9.6 hours. Over the same time period, the CTBT infrasound station IS55, ~25 km from Erebus, detected ~115 of the >1000 locally observed eruptions with amplitude decreases of >100x. An additional ~200 eruptions were recorded during local infrasound downtime. This represents an unusually high level of activity from the Erebus lava lake, and while instrument noise influences the minimum observable amplitude each day, the eruption infrasound amplitudes may vary by ~3 orders of magnitude over the scale of minutes to hours. We use this heightened period of variable activity and associated seismic and acoustic waveforms to examine mechanisms for bubble formation and ascent, such as rise speed dependence and collapsing foam; repose times for the larger eruptions; and possible eruption connections to lava lake cyclicity.

  15. Infrasound associated with the deep M 7.3 northeastern China earthquake of June 28, 2002

    NASA Astrophysics Data System (ADS)

    Che, Il-Young; Kim, Geunyoung; Pichon, Alexis Le

    2013-02-01

    On 28 June, 2002, a deep-focus (566 km) earthquake with a moment magnitude of 7.3 occurred in the China-Russia-North Korea border region. Despite its deep focus, the earthquake produced an infrasound signal that was observed by the remote infrasound array (CHNAR), 682 km from the epicenter, in South Korea. Coherent infrasound signals were detected sequentially at the receiver, with different arrival times and azimuths indicating that the signals were generated both near the epicenter and elsewhere. On the basis of the azimuth, arrival time measurements, and atmospheric ray simulation results, the source area of the infrasonic signals that arrived earlier were located along the eastern coastal areas of North Korea and Russia, whereas later signals were sourced throughout Japan. The geographically-constrained, and discrete, distribution of the sources identified is explained by infrasound propagation effects caused by a westward zonal wind that was active when the event occurred. The amplitude of the deep quake's signal was equivalent to that of a shallow earthquake with a magnitude of approximately 5. This study expands the breadth of seismically-associated infrasound to include deep earthquakes, and also supports the possibility that infrasound measurements could help determine the depth of earthquakes.

  16. Combining Infrasound and Imaging Techniques to Characterize and Quantify Eruptive Activity at Karymsky Volcano, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Fee, D.; Lopez, T. M.; Rowell, C.; Matoza, R. S.; Szuberla, C.; Prata, F.; Firstov, P.; Makhmudov, E.

    2012-12-01

    Changes in atmospheric pressure at volcanic vents caused by the rapid release and expansion of volcanic material (e.g., gas, ash, lava) produce low frequency sound waves known as infrasound. Because of the direct link between the infrasound source and the eruption and emission of volcanic material, complementary direct and remote observations of gas, ash, and other eruptive phenomena can be combined with infrasound measurements to characterize and quantify volcanic activity. Here we present coincident measurements collected over two 10-day periods at Karymsky Volcano in August 2011 and July 2012 of infrasound, SO2, thermal radiation, ash (2011 only), and visual imagery. Infrasound and audible (up to 250 Hz) acoustic data were recorded using arrays of portable digital microphones. SO2 emissions were measured using both a scanning FLYSPEC ultraviolet spectrometer system as well as a CyClops infrared camera equipped with broadband, 8.6, 10, and 11 micron filters permitting detection and quantification of both SO2 and ash. A FLIR infrared camera was utilized to record high temporal resolution thermal observations of the volcanic emissions and hot eruption deposits. Lastly, visual imagery was taken with an HD camcorder. Correlations between this multiparameter dataset allow a better understanding of both the infrasound data and eruptive activity. Karymsky Volcano is one of the most active and dynamic volcanoes in Kamchatka, Russia, with activity during our experiments consisting of vigorous degassing, frequent ash explosions, apparent vent sealing, and intermittent explosive magmatic eruptions. This varied activity produced diverse acoustic and emissions signals. Large explosive eruptions in 2011 are preceded by vent sealing and produce high-amplitude infrasound with occasional visible shock waves. Vigorous gas jetting is also observed and accompanied by elevated SO2 emissions and low infrasound levels. The gas jetting produced clear audible sound (~20-100 Hz) that

  17. Characterization and diagnostic methods for geomagnetic auroral infrasound waves

    NASA Astrophysics Data System (ADS)

    Oldham, Justin J.

    Infrasonic perturbations resulting from auroral activity have been observed since the 1950's. In the last decade advances in infrasonic microphone sensitivity, high latitude sensor coverage, time series analysis methods and computational efficiency have elucidated new types of auroral infrasound. Persistent periods of infrasonic activity associated with geomagnetic sub-storms have been termed geomagnetic auroral infrasound waves [GAIW]. We consider 63 GAIW events recorded by the Fairbanks, AK infrasonic array I53US ranging from 2003 to 2014 and encompassing a complete solar cycle. We make observations of the acoustic features of these events alongside magnetometer, riometer, and all-sky camera data in an effort to quantify the ionospheric conditions suitable for infrasound generation. We find that, on average, the generation mechanism for GAIW is confined to a region centered about ~60 0 longitude east of the anti-Sun-Earth line and at ~770 North latitude. We note furthermore that in all cases considered wherein imaging riometer data are available, that dynamic regions of heightened ionospheric conductivity periodically cross the overhead zenith. Consistent features in concurrent magnetometer conditions are also noted, with irregular oscillations in the horizontal component of the field ubiquitous in all cases. In an effort to produce ionosphere based infrasound free from the clutter and unknowns typical of geophysical observations, an experiment was undertaken at the High Frequency Active Auroral Research Program [HAARP] facility in 2012. Infrasonic signals appearing to originate from a source region overhead were observed briefly on 9 August 2012. The signals were observed during a period when an electrojet current was presumed to have passed overhead and while the facilities radio transmitter was periodically heating the lower ionosphere. Our results suggest dynamic auroral electrojet currents as primary sources of much of the observed infrasound, with

  18. Infrasound product resources at the IRIS DMC

    NASA Astrophysics Data System (ADS)

    Bahavar, M.; Trabant, C.; Hutko, A. R.; Karstens, R.

    2012-12-01

    In 2011 infrasound sensors were installed at some existing USArray Transportable Array (TA) sites and became a standard component of all new sites. Currently there are over 400 sites with infrasound sensors with an average spacing of 70 kilometers. To promote and facilitate the use of these data the IRIS Data Management Center has developed two new data products: an infrasound reference event database and an infrasound signal detector. The TA Infrasound Reference Event Database (TAIRED) is a user-supported database that contains information on events of interest for which there are associated USArray microbarograph recordings. This database is initially populated with a few events from observations on the USArray infrasound data, event bulletins, news on explosions, meteorological events and rocket launches. As a user-supported resource, we ask users to submit events of interest to be included in the database or submit their alternate solutions to the existing events. The second data product is an infrasound signal detector that regularly scans the USArray broadband infrasound data (BDF channel sampled at 40 Hz) and produces detections that highlight time intervals containing potential signals of interest. The detection product includes two components, standard signal-to-noise ratio based detections and spectral power based detections. No attempt is made to categorize detections or associate them to events. These data products join the growing collection of products produced and managed at the IRIS DMC, for the complete list please visit http://www.iris.edu/dms/products/.

  19. Modeling the Infrasound Acoustic Signal Generation of Underground Explosions at the Source Physics Experiment

    NASA Astrophysics Data System (ADS)

    Whitaker, R. W.; Jones, K. R.; Arrowsmith, S.

    2013-12-01

    One of the primary goals of the Source Physics Experiment is to improve upon and develop new physics based models for underground nuclear explosions using scaled, underground chemical explosions as proxies. Jones et. al, (AGU 2012) previously presented results describing the use of the Rayleigh integral (RI) to model the source region of the SPE explosions. While these results showed that the source region could be modeled using the RI, there were some complexities in the produced, synthetic waveforms that were unaccounted for when compared to the observed data. To gain insight into these complexities and to verify the results of the RI method, we used CAVEAT, a two-dimensional computational fluid dynamics, time-domain finite-difference code developed at Los Alamos National Labs (LANL). CAVEAT has been used in the solution of high speed and low speed fluid problems. While the RI uses the observed acceleration records from the 12 vertical surface accelerometers installed above ground zero, CAVEAT employs a synthetic source-time function, based on the acceleration records, that varies with range and time. This model provides a velocity boundary condition at the bottom boundary of the CAVEAT computation mesh that drives the atmospheric pressure wave into the atmosphere.

  20. The source of infrasound associated with long-period events at mount St. Helens

    USGS Publications Warehouse

    Matoza, R.S.; Garces, M.A.; Chouet, B.A.; D'Auria, L.; Hedlin, M.A.H.; De Groot-Hedlin, C.; Waite, G.P.

    2009-01-01

    During the early stages of the 2004-2008 Mount St. Helens eruption, the source process that produced a sustained sequence of repetitive long-period (LP) seismic events also produced impulsive broadband infrasonic signals in the atmosphere. To assess whether the signals could be generated simply by seismic-acoustic coupling from the shallow LP events, we perform finite difference simulation of the seismo-acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere. The effects of topography, velocity structure, wind, and source configuration are considered. The simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of P/SV and Rayleigh wave energy converted locally along the propagation path, and acoustic energy originating from , the source epicenter. Although the horizontal acoustic velocity of the latter is consistent with our data, the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations, and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source. The observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic LP events. The observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated, highly permeable material. Heating by magmatic activity causes pressure to rise, periodically reaching the pressure threshold for rupture of the "valve" sealing the crack. Sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack, initiating resonance of the remaining fluid. Subtle waveform and amplitude variability of the infrasonic signals as

  1. Ground motions and the infrasound signal: A new model and the discovery of a significant cavity rebound signal. Los Alamos Source Region Program

    SciTech Connect

    Jones, E.M.; App, F.N.; Whitaker, R.W.

    1993-03-01

    A model is presented that relates infrasound signals from underground nuclear tests to the peak vertical velocity at surface-ground-zero. For the most part, agreement between the model and observations is good, the exceptions being events conducted in shallow tuff layers in Yucca Flat. These events all have low values of the peak surface velocity. The authors have determined that the lack of agreement for these events is due to an unusual, second spall event. A stress-wave calculation is presented that reproduces the second-spall phenomenon and indicates that it is due to interference of cavity-rebound-associated signal with the initial ballistic motion of the surface layers. The effect of the rebound signal is to increase the amplitude of the infrasound signal and thus make low velocity events more detectable.

  2. Recent development of infrasound monitoring network in Romania

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela; Popa, Mihaela; Ionescu, Constantin

    2017-04-01

    The second half of 2016 was marked at National Institute for Earth Physics (NIEP) by a significant development of infrasound monitoring infrastructure in Romania. In addition to IPLOR, the 6-element acoustic array installed at Plostina, in the central part of Romania, since 2009, two other four-element arrays were deployed. The first one, BURARI infrasound research array, was deployed in late July 2016, under a joint effort of AFTAC, USA and NIEP, in the northern part of Romania, in Bucovina region. The sites, placed in vicinity of the central elements of BURAR seismic array (over 1.2 km aperture), are equipped with Chaparral Physics Model 21 microbarometers and Reftek RT 130 data loggers. The data, used mainly for research purposes within the scientific collaboration project between NIEP and AFTAC, are available to scientific community. The second one is a PTS portable infrasound array (I67RO) deployed for one year, starting with the end of September 2016, within a collaboration project between NIEP and PTS of the Preparatory Commission for CTBTO. This array is located in the western part of Romania, at Marisel, Cluj County, covering a 0.9 km aperture and being equipped with CEA/DAM MB2005 microbarometers and Reftek RT 130 data loggers. This joint experiment aims to contribute both to advanced understanding of infrasound sources in Central-Europe and to ARISE design study project, as an expansion of the spatial coverage of the European infrasound network. The data recorded by the three infrasound arrays deployed in Romania, during a same time interval (October - December 2016) were processed into detection arrival bulletins applying CEA/DASE PMCC algorithm embedded in DTK-GPMCC (extended CTBTO NDC-in-a-box) and WinPMCC software applications. The results were plotted and analyzed using DTK-DIVA software (extended CTBTO NDC-in-a-box), in order to assess detectability of each station, as well as the capacity of fusing detections into support of infrasound monitoring

  3. GNSS-TEC observations of infrasound excited by a volcanic eruption: Inference of wave front geometry and acoustic wave energy

    NASA Astrophysics Data System (ADS)

    Nakashima, Y.; Aoki, Y.; Nishida, K.; Heki, K.

    2016-12-01

    Volcanic eruptions excite various oscillations depending on various factors. Very low frequency infrasound (-5 mHz) can reach the upper atmosphere and are often observed as ionospheric fluctuations. We can see three types of ionospheric disturbances excited by volcanic eruptions: (1) acoustic trap mode, (2) atmospheric internal gravity wave and (3) traveling acoustic waves come from volcanic explosion. The third one is important to improve our knowledge of acoustic energy by volcanic explosions because we cannot detect infrasound propagating upward by barometers deployed on the ground. We found ionospheric disturbances made by the Kuchinoerabujima volcano eruption on 29 May, 2015, using the GNSS-TEC method. This case is similar to the 2004 Asamayama volcano explosion, and we tried to estimate the energy of the acoustic wave. In this presentation, we will compare TEC perturbations and surface pressure changes. We use 1 Hz-sampled GEONET data from stations in Southwest Japan. Conversion from slant-TEC to vertical-TEC was done using the minimum scalloping. We used apparent velocities calculated from cross correlation function of the TEC disturbances to infer the wave front geometry. Previous studies discussed wave fronts calculated by ray-tracing. However, ray tracing may be inappropriate to such a case because it assumes very short wave length compared with the scale height. Accordingly, we estimated the incident angles from the apparent wave velocities assuming that the ionosphere is a thin layer located at 300 km above the surface. We derived incident angles, and they were similar to those we obtained by ray tracing. In addition, we found that the incident angles inferred in this way had significant dependence on azimuths. We need to find out whether it is real or an apparent phenomenon caused by stations-satellites-wave geometry. We are now trying to estimate the energy, but it varies around the estimated value for the 2004 Asama volcano case. We will consider the

  4. Databases for Studies of Infrasound Propagation in the European Arctic

    NASA Astrophysics Data System (ADS)

    Gibbons, Steven J.; Ringdal, Frode

    2010-05-01

    Industrial and military sources in northern Fennoscandia and NW Russia generate both seismic and infrasound signals observed at regional distances. Similar seismic signals constrain origin times and explosion yield and, using correlation detectors at the ARCES array, have enabled us to detect and classify hundreds of events from a small number of sites. This has in turn provided superb datasets for infrasound propagation studies. The multi-channel waveform correlation procedure has even had considerable success in detecting closely spaced events when the signals from subsequent events show considerable differences. A post-processing system which examines the alignment of the single-channel cross-correlation traces allows for very low detection thresholds with low false alarm rates. Near-surface explosions at Hukkakero in northern Finland generate infrasound signals on the seismic sensors at ARCES, 175 km to the North, near to the edge of the classical "Zone of Silence". Many tropospheric phase observations can be predicted using ray-tracing given favourable winds at low altitudes. However, the vast majority of the observed infrasound signals - probably refracted from stratospheric heights - are not predicted by ray-tracing, warranting a re-evaluation of propagation models for these distances. In 2008, a mini-array of microbarographs, co-located with ARCES seismometers, also observed later signals probably refracted from thermospheric heights. These signals are more impulsive and of smaller amplitude than the more typically observed signals. A second site near the northern coast of the Kola Peninsula is approximately 250 km from ARCES to the West and Apatity to the South. Despite poor waveform similarity between events, multichannel correlation detectors assign confidently over 350 events over an 8 year period to this site. Infrasound is observed at ARCES for almost all events in the summer and almost no events in the winter, and is observed at Apatity for almost

  5. Assessing and optimizing infrasound network performance: application to remote volcano monitoring

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Le Pichon, Alexis; Marchetti, Emanuele; Ceranna, Lars; Pilger, Christopher

    2015-04-01

    Interest in infrasound propagation studies has been revived since the Comprehensive nuclear Test Ban Treaty (CTBT) was adopted in 1996. The International Monitoring System (IMS) is designed to ensure compliance with the CTBT by detecting and locating explosions in the world using at least 2 stations. Even not yet fully established, the infrasound network already allows studies on a global scale as it has demonstrated to be a major asset to remotely identify and analyze geophysical events such as volcanoes. Simulation methods incorporating realistic source and propagation effects have been developed to quantify the detection capability of this network. These methods can also be used to optimize the network configuration (number of stations, geographical location) in order to reduce the detection thresholds taking into account seasonal effects in infrasound propagation. Recent studies have shown that remote infrasound observations can provide useful information about eruption chronology and the released acoustic energy. Comparisons with near-field recordings allow evaluating the potential of these observations to better constrain source parameters when other monitoring techniques (satellite, seismic, gas) are not available or cannot be made. Because of its regular activity, the well-instrumented Mount Etna is in Europe a unique natural repetitive source to test and optimize detection and simulation methods. In summer, during the downwind season, its eruptions are quasi-permanently detected by IS48 in Tunisia, the closest infrasound station part of the IMS. Under the European ARISE project (Atmospheric dynamics InfraStructure in Europe, FP7/2007-2013), experimental arrays have been installed in order to characterize infrasound propagation in different ranges of distance and direction. Such an experimental setting offers an opportunity to address the societal benefits that can be achieved through routine infrasound monitoring.

  6. Listening to Earthquakes with Infrasound

    NASA Astrophysics Data System (ADS)

    Mucek, A. E.; Langston, C. A.

    2011-12-01

    A tripartite infrasound array was installed to listen to earthquakes occurring along the Guy-Greenbrier fault in Arkansas. The active earthquake swarm is believed to be caused by deep waste water injections and will allow us to explain the mechanisms causing earthquake "booms" that have been heard during an earthquake. The array has an aperture of 50 meters and is installed next to the X301 seismograph station run by the Center for Earthquake Research and Information (CERI). This arrangement allows simultaneous recording of seismic and acoustic changes from the arrival of an earthquake. Other acoustic and seismic sources that have been found include thunder from thunderstorms, gunshots, quarry explosions and hydraulic fracturing activity from the local gas wells. The duration of the experiment is from the last week of June to the last week of September 2011. During the first month and a half, seven local earthquakes were recorded, along with numerous occurrences of the other infrasound sources. Phase arrival times of the recorded waves allow us to estimate wave slowness and azimuth of infrasound events. Using these two properties, we can determine whether earthquake "booms" occur at a site from the arrival of the P-wave or whether the earthquake "booms" occur elsewhere and travel through the atmosphere. Preliminary results show that the infrasound correlates well to the ground motion during an earthquake for frequencies below 15 Hertz.

  7. Eruptions of Mount Erebus Volcano Constrained with Infrasound, Video, and Doppler Radar

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Jones, K. R.; Aster, R.; Kyle, P.; McIntosh, W.; Gerst, A.

    2008-12-01

    Co-eruptive infrasound recorded within several km of volcanoes can provide effective constraints on atmospheric accelerations or momentum exchange in the vicinity of active volcanic vents. These atmospheric perturbations can be induced by impulsive gas injection into the atmosphere (i.e., eruptive explosions), by deflection of a solid or fluid lava surface, or through a superposition of these effects. The "simple" lava lake bubble-bursting eruptions of Mount Erebus Volcano (Antarctica) provide an ideal test bed for multi- disciplinary observations of volcanic infrasound because of proximal (within few hundred meters) deployment of microphones and line-of-sight viewing geometry of cameras and radar to the vent. Erebus video observations provide timing constraints on the infrasound generation mechanisms, which include both pre- eruptive distension of the lava lake surface and gas expansion and jetting following large explosive bubble bursts. Network infrasound recordings are used to quantify the time history of explosive gas flux and cumulative yield (>103 kg of gas in ~0.5 s), which is corroborated by the video and Doppler radar observations. Infrasound records from a three-station network also show azimuthal variations, which can be attributed to non-isotropic components of the acoustic wavefield radiated during eruption. We model Erebus gas bubble bursts as a combination of symmetric gas expansion (monopole source) and gas jetting (dipole source) and corroborate this explosive asymmetry with video and Doppler radar observations.

  8. Simulation and Analysis of Infrasound Generated by Convective Storms and Tornadoes

    NASA Astrophysics Data System (ADS)

    Schecter, D.; Nicholls, M.

    2011-12-01

    Observational studies have shown that severe storms can emit abnormally strong, sustained infrasound in the 0.5-5 Hz frequency range. There is reason to believe that the infrasonic emissions come from developing and mature tornadoes, but some ambiguity remains in the interpretation of the data. It is fair to say that we do not yet fully understand the conditions for which a vortex signal is discernible from the infrasound of non-tornadic sources within a storm. There is a pressing need to advance our fundamental understanding of the different mechanisms that generate infrasound in atmospheric convection. To this end, numerical modeling may be the best method of investigation. We are exploring this avenue of research with a customized version of the Regional Atmospheric Modeling System (c-RAMS). Previous studies have established the basic credibility of c-RAMS for simulating acoustic phenomena. More recently, we have developed a convenient method for diagnosing the primary sources of infrasound in complex storm simulations. The method is based on a generalization of Lighthill's acoustic analogy, and is aptly illustrated in the context of a simulated cumulonimbus. Applying the diagnostic method to this system, we find that the 0.1-1 Hz infrasound of diabatic processes in the hail-to-rain transition layer dominates that of turbulent wind fluctuations covering the entire storm. We have also used c-RAMS to investigate the infrasound of tornadoes created by artificial buoyancy forcing in a dry, rotational environment. The simulated tornadoes have realistic structure, but their cores are typically quiet in the frequency range of interest. In other words, we find that dry fluctuations of the vortex core may not provide a robust source of discernible infrasound. Apparent deficiencies of earlier theories that predicted otherwise will be addressed. This work was supported by NSF grant AGS-0832320.

  9. Characterization of the 2008 Kasatochi and Okmok eruptions using remote infrasound arrays

    NASA Astrophysics Data System (ADS)

    Fee, David; Steffke, Andrea; Garces, Milton

    2010-01-01

    The 2008 Plinian eruptions of Kasatochi and Okmok volcanoes were recorded by six remote International Monitoring System infrasound arrays. High-amplitude infrasound at these stations, combined with remote sensing, permits insight into important volcanic source parameters, such as origin times, durations, and source characteristics. Infrasound from the 7-8 August Kasatochi eruption consists of three well-defined eruption pulses, with the first two steam-rich and the last ash-rich. Pulse 2 is the most energetic and impulsive. Okmok produced over 9 h of continuous infrasound on 12-13 July. Acoustic propagation modeling for the Okmok eruption and first Kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations. However, theoretical acoustic origin times of pulses 2-3 are predicted to occur ˜15 min earlier than the seismic. Stratospheric ducting for these later pulses provides more consistent origin times. Although both volcanoes ejected ash into the stratosphere (>15 km), Kasatochi produced higher amplitude infrasound than Okmok. Previous studies have shown sustained infrasound with frequencies <0.5 Hz is indicative of high-altitude ash emissions. Kasatochi and Okmok recordings are consistent with this, as stratospheric emissions evident in satellite imagery are correlated with sustained 0.01-0.5 Hz infrasound. Further, the acoustic spectrum shape resembles the spectrum from man-made jets, suggesting a self-similar noise generation mechanism proposed in earlier work. Although uncertainties exist, observations and propagation modeling from Kasatochi suggest self-similarity is apparent at long distances (>2000 km) and does not seem to be appreciably affected by changes in ash content between the eruption pulses.

  10. Volcano infrasound: A review

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey Bruce; Ripepe, Maurizio

    2011-09-01

    Exploding volcanoes, which produce intense infrasound, are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade. Volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent, as opposed to seismic signals, which are generated by both surface and internal volcanic processes. As with seismology, infrasound can be recorded remotely, during inclement weather, or in the dark to provide a continuous record of a volcano's unrest. Moreover, it can also be exploited at regional or global distances, where seismic monitoring has limited efficacy. This paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity. Many infrasound studies have focused on integration with other geophysical data, including seismic, thermal, electromagnetic radiation, and gas spectroscopy and they have generally improved our understanding of eruption dynamics. Other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk. This paper aims to provide an overview of volcano airwave studies (from analog microbarometer to modern pressure transducer) and summarizes how infrasound is currently used to infer eruption dynamics. It also outlines the relative merits of local and regional infrasound surveillance, highlights differences between array and network sensor topologies, and concludes with mention of sensor technologies appropriate for volcano infrasound study.

  11. Recent Advances in Infrasound Science for National Security Applications

    NASA Astrophysics Data System (ADS)

    Arrowsmith, S.; Blom, P. S.; Marcillo, O. E.; Whitaker, R. W.

    2014-12-01

    Infrasound is sound below the frequency-threshold of human hearing, covering the frequency range from 0.01 - 20 Hz. Infrasound science studies the generation, propagation, measurement, and analysis of infrasound. Sources of infrasound include a wide variety of energetic natural and manmade phenomena that include chemical and nuclear explosions, rockets and missiles, and aircraft. The dominant factors influencing the propagation of infrasound are the spatial and temporal variations in temperature, wind speed, and wind direction. In recent years, Infrasound Science has experienced a renaissance due to the installation of an international monitoring system of 60 infrasound arrays for monitoring the Comprehensive Nuclear Test Ban Treaty, and to the demonstrated value of regional infrasound networks for both scientific and applied purposes. Furthermore, in the past decade, significant advances have been made on using measurements of infrasound to invert for these properties of the atmosphere at altitudes where alternative measurement techniques are extremely costly. This presentation provides a review of recent advances in infrasound science as relevant to National Security applications.

  12. Detecting geyser activity with infrasound

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Anderson, J. F.; Anthony, R. E.; Sciotto, M.

    2013-04-01

    We monitored geyser activity in the Lower Geyser Basin (LGB) of Yellowstone National Park with dual four-element microphone arrays separated by ~ 600 m. The arrays were independently used to identify incident coherent plane wave energy, then conjoint cross beam back-azimuths from the two arrays were used to precisely locate signal sources. During a week in August 2011 we located repeating infrasound events, peaked in energy between 1 and 10 Hz, originating from at least five independent geothermal features, including the episodically erupting Great Fountain, Fountain and Kaleidoscope Geysers, as well as periodic infrasound from nearby Botryoidal and persistent sound from Firehole Spring. Although activity from nearby cone-type geysers was not detected in the infrasound band up through 50 Hz, the major fountain-type geysers (i.e., with columns greater than 10 m) could be detected at several kilometers, and two minor geysers (i.e., a few meters in eruption height) could be tracked at distances up to a few hundred meters. Detection of geyser activity was especially comprehensive at night when ambient noise was low. We conclude that infrasound monitoring of fountain-type geysers permits convenient tracking of geyser activity, episodicity, signal duration, energy content, and spectral content. These parameters enable objective statistical quantification of geyser behavior and changes over time that may be due to external forcing. Infrasonic study of geyser activity in an individual basin has great monitoring utility and can be reasonably accomplished with two or more distributed sensor arrays.

  13. IPLOR performance in detecting infrasound from volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela; Popa, Mihaela

    2016-04-01

    Plostina infrasound array (IPLOR) is located in the central part of Romania, in Vrancea region, its current configuration consisting of 6 elements equipped with Chaparral Physics sensors deployed over a 2.5 km aperture. The array detectability observed after processing of more than 6 years of data has shown that IPLOR is more effective in measuring mainly infrasound signals produced by natural and anthropogenic impulsive sources. This can be explained by the sensors' characteristics (frequency response, dynamic range) and the large aperture of array. Among the types of events observed with IPLOR, an emphasis can be given to the Mt. Etna volcanic eruptions as one of the powerful infrasound source recorded by the array. Located at about 1320 km distance from volcano, the array has proved efficient in observing both large and small eruptions. In case of the most large eruptive episodes occurred lately (April and October 2013, December 2015), long duration infrasonic signals were detected, the initial impulsive signature of the volcanic explosion being followed by a long train of irregular waves with smaller amplitudes and higher frequency, extended over periods ranging from 6 hours to more than three days (in December 2015). For the purpose of assessing the IPLOR performance in detecting Etna eruptions, the signal interactive analysis was performed using WinPMCC, CEA/DASE version of PMCC software. The infrasound detections obtained were plotted in function of back-azimuth, velocity and frequency, showing that the detectability is dependent both on the diurnal variations of the noise around the array (during the night the human activity diminishes) and on the seasonally dependent stratospheric winds (westward propagation during summer and eastward propagation during winter). In case of the Etna eruptive episodes detected by IPLOR, the back azimuth observed is in good agreement with the expected value (230o), i.e. an average value of 232±2o could be resolved. The

  14. Infrasound observation of the apparent North Korean nuclear test of 25 May 2009

    NASA Astrophysics Data System (ADS)

    Che, Il-Young; Kim, Tae Sung; Jeon, Jeong-Soo; Lee, Hee-Il

    2009-11-01

    On 25 May 2009, a seismic event (mb 4.6) was recorded from a source in northeastern North Korea, close to the location of a previous seismic event on 9 October 2006. Both events have been declared to be nuclear tests by North Korea. For the more recent test, five seismo-acoustic arrays in South Korea recorded epicentral infrasonic signals. The signals are characterized by amplitudes from 0.16 to 0.35 microbar and dominant frequencies between 0.8 and 4.3 Hz. Celerities determined for the arrivals suggest that most of the infrasonic energy travelled as a stratospheric phase. Based on observed stratospheric amplitudes, the epicentral infrasonic energy was estimated to be equivalent to that expected from 3.0 tons of high explosives detonated on the surface. We conclude that this small energy estimate is due to the atmospheric coupling from the strong surface ground motion rather than the direct transfer of explosion energy to the air. This relatively small infrasonic to seismic energy ratio could be used to distinguish the event from a common surface explosion.

  15. Evaluation of infrasound sensors

    SciTech Connect

    Kromer, R.P.; McDonald, T.S.

    1998-08-01

    Sandia is evaluating the performance of various infrasound sensors that could be used as part of the International Monitoring Systems (IMS). Specifications for infrasound stations are outlined in CTBT/PC/II/1/Add.2. This document specifies minimum requirements for sensor, digitizer and system. The infrasound sensors evaluation task has the following objectives: provide an overview of the sensors presently in use; evaluate these sensors with respect to the requirements of the IMS.

  16. Infrasound Sensor Coverage at Regional Ranges as driven by the Atmospheric State

    NASA Astrophysics Data System (ADS)

    Norris, D.

    2010-12-01

    Infrasound is an attractive regional sensor modality in explosion monitoring applications due to its non line-of-sight, long-range detection capability. Anthropomorphic activity, including impulsive events such as explosions and continuous events such as vehicle operation, can be routinely detected over tens of kilometer ranges and beyond. This study addresses the issues associated with effectively leveraging infrasound for regional monitoring applications. A key challenge in applying infrasound at these ranges is adequately understanding the propagation. Spatial and temporal features of the atmospheric state create evolving regions of acoustic focusing and shadowing at the surface. Understanding this acoustic "footprint" and having the capability to predict it over time is necessary for two reasons. It drives the planning process of where to deploy a given permanent or temporary suite of infrasound sensors. In addition, knowing the observability of a stationary or mobile source supports the interpretation of operational data. This research includes a sample study on characterization of atmospheric effects on regionally deployed infrasound networks. Predictions are made from real atmospheric states to illustrate the range of observability conditions that may occur. It was found that the observability can have significant frequency dependence.

  17. Infrasound research at Kola Regional Seismological Centre, Russia

    NASA Astrophysics Data System (ADS)

    Asming, Vladimir; Kremenetskaya, Elena

    2013-04-01

    A small-aperture infrasound array has been installed in Kola Peninsula, Russia 17 km far from the town of Apatity in the year 2000. It comprises 3 Chaparral V microbarographs placed closely to the APA seismic array sensors and equipped with pipe wind reducing filters. The data are digitized at the array site and transmitted in real time to a processing center in Apatity. To search for infrasound events (arrivals of coherent signals) a beamforming-style detector has been developed. Now it works in near real time. We analyzed the detecting statistics for different frequency bands. Most man-made events are detected in 1-5 Hz band, microbaromes are typically detected in 0.2-1 Hz band. In lower frequencies we record mostly a wind noise. A data base of samples of infrasound signals of different natures has been collected. It contains recordings of microbaromes, industrial and military explosions, airplane shock waves, infrasound of airplanes, thunders, rocket launches and reentries, bolides etc. The most distant signals we have detected are associated with Kursk Magnetic Anomaly explosions (1700 km far from Apatity). We implemented an algorithm for association of infrasound signals and preliminary location of infrasound events by several arrays. It was tested with Apatity data together with data of Sweden - Finnish infrasound network operated by the Institute of Space Physics in Umea (Sweden). By agreement with NORSAR we have a real-time access to the data of Norwegian experimental infrasound installation situated in Karasjok (North Norway). Currently our detection and location programs work both with Apatity and Norwegian data. The results are available in Internet. Finnish militaries routinely destroy out-of-date weapon in autumns at the same compact site in North Finland. This is a great source of repeating infrasound signals of the same magnitude and origin. We recorded several hundreds of such explosions. The signals have been used for testing our location routines

  18. Infrasound Calibration Experiment at Sayarim, Israel: preliminary tests

    NASA Astrophysics Data System (ADS)

    Gitterman, Y.; Hofstetter, A.; Garces, M.; Bowman, J. R.; Fee, D.; Israelsson, H.

    2009-12-01

    We are establishing a Ground Truth (GT0) infrasound dataset for Middle East/Mediterranean region, through conducting a series of surface explosions at Sayarim Military Range (SMR), Negev desert, which culminated with an 82-ton explosion in August 2009. The dataset will be used to characterize the infrasonic propagation in the region, depending on source features and atmosphere conditions, and thus to improve monitoring capabilities of International Monitoring System (IMS). Test explosions of broad yield range and various designs were conducted on the first stage, in different days and seasons, thus providing a wide range of atmospheric conditions. The goals were to: 1) test charge design and assembling, and train procedures of logistics and coordination, for preparation and conducting of the main explosion; 2) analyze atmospheric effects on infrasound propagation in different azimuths based on collected meteo-data. In June-July 2008, we conducted a series of 13 detonations of outdated ammunition (in the range 0.2-10 ton) and two experimental shots of 1 ton of different explosives (TNT and Composition B). The two shots were placed close to an ammunition explosion and 10 min afterwards to help estimate ammunition actual yield (TNT). Some of these explosions were observed at IMS station I48TN (Tunisia) at ~2500 km, using array processing and analysis. Two test explosions of 1 ton and 5 tons of different recuperated HE explosives were conducted at SMR in December 2008. High-pressures in air-shock waves at close distances (150-250 m) were measured and speed video recording was done. The data obtained from the test series provided estimation of the explosion yield, that showed approximate TNT equivalency. We analyzed signals from the tests, recorded on seismic and acoustic channels at near-source and local distances. We compared energy generation for different explosives, including cratering conditions, and investigated the influence of wind direction on infrasound

  19. Seismic and Infrasound Characteristics of North Korean Nuclear Explosions Utilizing Regional Data

    NASA Astrophysics Data System (ADS)

    Stump, B. W.; Park, J.; Che, I. Y.; Hayward, C.

    2016-12-01

    This work analyzes seismic and infrasound signals from four underground nuclear tests by North Korea in 2006, 2009, 2013, and 2016. Regional data from eight seismo-acoustic arrays, operated by Southern Methodist University (SMU) and Korea Institute of Geosciences and Mineral Resources (KIGAM) located in the Korean peninsula, a seismic station in China (MDJ), and two nearby International Monitoring System (IMS) infrasound arrays in Russia (IS45) and Japan (IS30) are used. Infrasound signals at the arrays are detected using the progressive multi-channel correlation (PMCC; Cansi, 1995) followed by analyst review and compared to model predictions based on the method of Blom and Waxler (2012) using Ground-to-Space (G2S) specifications (Drob et al., 2003). This comparison documents that infrasound detection and event locations are dependent on the atmospheric conditions and local noise levels at the time of each explosion. Based on empirical yield-scaling relation of Whitaker et al. (2003), infrasound source energies are estimated at the closest array (KSGAR) to be 0.6, 23.5, and 8.2 tons of TNT for 2009, 2013, and 2016, respectively (no clear observations from 2006). The relative seismic source scaling of the four explosions is assessed using Mueller and Murphy source model (1971) based upon regional seismic station spectral ratios of Pn, Pg, Sn, and Lg. Using a grid search method, we explore the range of acceptable source models in terms of depth of burial and yields for 2009/2006, 2013/2006, 2016/2006, 2013/2009, 2016/2009, and 2013/2016. Using this methodology the 2013/2016-yield ratio is from 1.05-1.30 with an estimated depth range from 0.71-1.15. The small infrasound yield is a reflection of the fact that the infrasound signal is a result of coupling from strong ground motion directly above the explosion and the atmosphere. Differences in relative yield ratios for seismic and infrasound provide constraints on source depth as well as free surface interactions.

  20. Recent Infrasound Calibration Activity at Los Alamos

    NASA Astrophysics Data System (ADS)

    Whitaker, R. W.; Marcillo, O. E.

    2014-12-01

    Absolute infrasound sensor calibration is necessary for estimating source sizes from measured waveforms. This can be an important function in treaty monitoring. The Los Alamos infrasound calibration chamber is capable of absolute calibration. Early in 2014 the Los Alamos infrasound calibration chamber resumed operations in its new location after an unplanned move two years earlier. The chamber has two sources of calibration signals. The first is the original mechanical piston, and the second is a CLD Dynamics Model 316 electro-mechanical unit that can be digitally controlled and provide a richer set of calibration options. During 2008-2010 a number of upgrades were incorporated for improved operation and recording. In this poster we give an overview of recent chamber work on sensor calibrations, calibration with the CLD unit, some measurements with different porous hoses and work with impulse sources.

  1. Interactions between intermittent gravity waves and infrasounds

    NASA Astrophysics Data System (ADS)

    Ribstein, Bruno; Millet, Christophe; Lott, Francois; de La Camara, Alvaro

    2016-11-01

    Even though the accuracy of atmospheric specifications is constantly improving, it is well known that the main part of gravity waves is still yet not resolved in the available data. In most infrasound modeling studies, the unresolved gravity wave field is often represented as a deterministic field that is superimposed on a given average background state. Direct observations in the lower stratosphere show, however, that the gravity wave field is very intermittent, and is often dominated by rather well defined wave packets. In this study we sample the gravity wave spectrum by launching few monochromatic waves and choose their properties stochastically to mimic the intermittency. The statistics of acoustic signals are computed by decomposing the original signal into a sum of modal pulses. Owing to the disparity of the gravity and acoustic lengthscales, the interaction can be described using a multiplescale analysis and the appropriate amplitude evolution equation involves certain random terms that are related to the gravity wave sources. More specifically, it is shown how the unpredictable low level small-scale dynamics triggers multiple random stratospheric waveguides in which high frequency infrasound components can propagate efficiently.

  2. Overview of IMS infrasound station and engineering projects

    NASA Astrophysics Data System (ADS)

    Marty, J.; Doury, B.; Kramer, A.; Martysevich, P.

    2015-12-01

    The Provisional Technical Secretariat (PTS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBTO) has a continuous interest in enhancing its capability in acoustic source detection, localization and characterization. The infrasound component of the International Monitoring System (IMS) constitutes the only worldwide ground-based infrasound network. It consists of sixty stations, among which forty-eight are already certified and continuously transmit data to the International Data Centre (IDC) in Vienna, Austria. Each infrasound station is composed of an array of infrasound sensors capable of measuring micro-pressure changes produced at ground level by infrasonic waves. The characteristics of infrasonic waves are computed in near real-time by IDC automatic detection software and are used as an input to IDC source categorization and localization algorithms. The PTS is continuously working towards the completion and sustainment of the IMS infrasound network. The objective of this presentation is to review the main activities performed in the IMS infrasound network over the last five years. This includes construction, installation, certification, major upgrade and revalidation activities. Major technology development projects to improve the reliability and robustness of IMS infrasound stations as well as their compliance with IMS Operational Manual requirements will also be presented. This includes advances in array geometry, wind noise reduction, system calibration, meteorological data as well as power and communication infrastructures. Finally the impact of all these changes on the overall detection capability of the IMS infrasound network will be highlighted.

  3. Infrasound's capability to detect and characterise volcanic events, from local to regional scale.

    NASA Astrophysics Data System (ADS)

    Taisne, Benoit; Perttu, Anna

    2017-04-01

    Local infrasound and seismic networks have been successfully used for identification and quantification of explosions at single volcanoes. However the February, 2014 eruption of Kelud volcano, Indonesia, destroyed most of the local monitoring network. The use of remote seismic and infrasound sensors proved to be essential in the reconstruction of the eruptive sequence. The first recorded explosive event, with relatively weak seismic and infrasonic signature, was followed by a 2 hour sustained signal detected as far away as 11,000 km by infrasound sensors and up to 2,300 km away by seismometers. The volcanic intensity derived from these observations places the 2014 Kelud eruption between the intensity of the 1980 Mount St. Helens and the 1991 Pinatubo eruptions. The use of remote seismic stations and infrasound arrays in deriving valuable information about the onset, evolution, and intensity of volcanic eruptions is clear from the Kelud example. After this eruption the Singapore Infrasound Array became operational. This array, along with the other regional infrasound arrays which are part of the International Monitoring System, have recorded events from fireballs and regional volcanoes. The detection capability of this network for any specific volcanic event is not only dependent on the amplitude of the source, but also the propagation effects, noise level at each station, and characteristics of the regional persistent noise sources (like the microbarum). Combining the spatial and seasonal characteristics of this noise, within the same frequency band as significant eruptive events, with the probability of such events to occur, gives us a comprehensive understanding of detection capability for any of the 750 active or potentially active volcanoes in Southeast Asia.

  4. Infrasound emission generated by wind turbines

    NASA Astrophysics Data System (ADS)

    Ceranna, Lars; Pilger, Christoph

    2014-05-01

    Aerodynamic noise emissions from the continuously growing number of wind turbines in Germany are creating increasing problems for infrasound recording systems. Such systems are equipped with highly sensitive micro pressure sensors, which are accurately measuring acoustic signals in a frequency range inaudible to humans. At infrasound station IGADE, north of Bremen, a constantly increasing background noise has been observed throughout the years since its installation in 2005. The spectral peaks are reflecting well the blade passing harmonics, which vary with prevailing wind speeds. Overall, a decrease is noted for the infrasound array's detection capability. This aspect is particularly important for the other two sites of the German infrasound stations I26DE in the Bavarian Forest and I27DE in Antarctica, because plans for installing wind turbines near these locations are being under discussion. These stations are part of the International Monitoring System (IMS) verifying compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), and have to meet stringent specifications with respect to infrasonic background noise. Therefore data obtained during a field experiment with mobile micro-barometer stations for measuring the infrasonic pressure level of a single horizontal-axis wind turbine have been revisited. The results of this experiment successfully validate a theoretical model which estimates the generated sound pressure level of wind turbines and makes it possible to specify the minimum allowable distance between wind turbines and infrasound stations for undisturbed recording. Since the theoretical model also takes wind turbine design parameters into account, suitable locations for planned infrasound stations outside the determined disturbance range can be found, which will be presented; and vice versa, the model calculations' results for fixing the minimum distance for wind turbines planned for installation in the vicinity of an existing infrasound array.

  5. Empirical Relationships from Regional Infrasound Signals

    NASA Astrophysics Data System (ADS)

    Negraru, P. T.; Golden, P.

    2011-12-01

    Two yearlong infrasound observations were collected at two arrays located within the so called "Zone of Silence" or "Shadow Zone" from well controlled explosive sources to investigate the long term atmospheric effects on signal propagation. The first array (FNIAR) is located north of Fallon NV, at 154 km from the munitions disposal facility outside of Hawthorne NV, while the second array (DNIAR) is located near Mercury NV, approximately 293 km south east of the detonation site. Based on celerity values, approximately 80% of the observed arrivals at FNIAR are considered stratospheric (celerities below 300 m/s), while 20% of them propagated as tropospheric waveguides with celerities of 330-345 m/s. Although there is considerable scatter in the celerity values, two seasonal effects were observed for both years; 1) a gradual decrease in celerity from summer to winter (July/January period) and 2) an increase in celerity values that starts in April. In the winter months celerity values can be extremely variable, and we have observed signals with celerities as low as 240 m/s. In contrast, at DNIAR we observe much stronger seasonal variations. In winter months we have observed tropospheric, stratospheric and thermospheric arrivals while in the summer mostly tropospheric and slower thermospheric arrivals dominate. This interpretation is consistent with the current seasonal variation of the stratospheric winds and was confirmed by ray tracing with G2S models. In addition we also discuss how the observed infrasound arrivals can be used to improve ground truth estimation methods (location, origin times and yield). For instance an empirical wind parameter derived from G2S models suggests that the differences in celerity values observed for both arrays can be explained by changes in the wind conditions. Currently we have started working on improving location algorithms that take into account empirical celerity models derived from celerity/wind plots.

  6. Assessing the detection capability of the global IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Vergoz, J.; Brachet, N.; Ceranna, L.; Green, D.; Evers, L.

    2008-12-01

    A global scale analysis based on available detection lists for all operating IMS infrasound stations confirms that the primary factor controlling signal detectability is the seasonal variability of the stratospheric wind circulation. At most arrays, near %80 of the detections in the 0.2 to 2 Hz bandpass are associated with propagation downwind of the dominant wind direction. The seasonal transition in the bearings and number of detections between easterly and westerly directions is presented. The observed detection capability of the IMS network is compared to the predicted one using near-real time atmospheric updates and station- dependent wind noise models. The influence of individual model parameters on the network performance is systematically assessed. At frequencies of interest for detecting atmospheric explosions (0.2 to 2 Hz), the simulations predict that explosions equivalent to ~500 t of TNT would be detected by at least two stations of the full IMS network at any time of the year. Comprehensive ground-truth databases provide a statistical approach for evaluating the potential of infrasound monitoring. Accidental explosions are analysed and used here as benchmark for validating the calculated threshold maps. Such studies would help to optimize the siting of infrasound arrays with respect to both the number and configuration in order to monitor infrasonic sources of interest. They are an important step to enable a successful monitoring regime for atmospheric or surface events to act as an effective verification tool in any future enforcement of the CTBT.

  7. Infrasound Studies of Alaskan Volcanoes

    NASA Astrophysics Data System (ADS)

    McNutt, S. R.; Arnoult, K.; Szuberla, C.; Olson, J. V.; Wilson, C. R.

    2010-12-01

    Infrasound has been used to study a number of Alaskan volcanic eruptions over the last 15 years. Arrays include the I53US array of 8 sensors in Fairbanks installed in 2002 under the CTBT umbrella; an array of 4 sensors installed at Okmok Volcano in summer 2010 by the Alaska Volcano Observatory (AVO); and a 6-sensor array installed in Dillingham in September 2010 by the UAF Infrasound Group. Individual sensors have been installed by AVO at Pavlof (1996), Shishaldin (1997), Augustine (2006), Fourpeaked (2006), and Redoubt (2009) volcanoes. These have been especially valuable because they provide precise source timing and signal strength that allow the correct identification of atmospheric paths. Small volcanic explosions have been recorded at local stations only for Pavlof, Shishaldin and Fourpeaked volcanoes. The more interesting large explosive eruptions have been recorded on both local stations and arrays from eruptions at Augustine in 2006 (13 events), Fourpeaked in 2006 (2 events), Cleveland in 2007 (1 event), Okmok in 2008 (1 sustained event), Kasatochi in 2008 (5 events), and Redoubt in 2009 (over 30 events). Pressures up to 6 Pa have been recorded for the largest Redoubt event at a distance of 547 km from the array, and 1.2 Pa for the largest Kasatochi event at a distance of 2104 km. We determined reduced pressures (equivalent pressure at 1 km assuming 1/r decay) and find that Kasatochi exceeds 2500 Pa and Redoubt 1600 Pa. The smaller explosive eruptions at Augustine yield reduced pressures of 40 to 300 Pa. There is reasonable correlation between measured pressures and signal durations and the ash cloud heights and tephra volumes, hence the infrasound data are useful for hazard assessment. However, the long travel times (3 sec per km) suggest that infrasound array data arrive too late for primary detection but are good for estimating other attributes such as size. Infrasound data may also be combined with seismic data to determine the partitioning of energy

  8. Spall Effects on Infrasound Generation

    NASA Astrophysics Data System (ADS)

    Jones, K. R.; Rodgers, A. J.; Whitaker, R. W.; Ezzedine, S. M.; Vorobiev, O.

    2014-12-01

    Spall effects from buried explosions are seen in near-source surface accelerations and depend on explosion yield, emplacement depth-of-burial and material strength. Investigations of infrasound from buried explosions have shown how atmospheric overpressure can be derived from surface acceleration through application of the Rayleigh Integral (Bannister, 1980). Recently, underground chemical explosions as part of the Source Physics Experiment (SPE) at the Nevada National Security Site (NNSS) have been shown to generate spall signatures in local-distance infrasound (Jones et al. 2014). We are investigating the effects of spall on infrasound generation using two approaches. The first approach uses the Rayleigh integral to compute overpressures for buried explosions from synthetic vertical acceleration data at surface ground zero. To obtain the synthetic surface accelerations we use reported models from nuclear explosion studies and systematically vary parameters such as the spall duration, depth of burial and magnitude. The effect on the resulting acoustic waveform shape will be investigated. The second method uses a hydrodynamic approach to more fully characterize the varied parameters to produce the acoustic waveforms. As the spall decreases we find that the acoustic waveform shape changes dramatically. This waveform signature may provide diagnostics on the explosive source and may be a useful metric for underground explosion monitoring. This work was done under award number DE-AC52-06NA25946. 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.

  9. Engineering and development projects for the sustainment and enhancement of the IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Marty, J.; Martysevich, P.; Kramer, A.; Haralabus, G.

    2012-04-01

    The Provisional Technical Secretariat (PTS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has a continuous interest in enhancing its capability in infrasound source localization and characterization. This capability is based on the processing of data recorded by the infrasound network of the International Monitoring System (IMS). This infrasound network consists of sixty stations, among which forty-five are already certified and continuously transmit data to the International Data Center (IDC) in Vienna, Austria. Each infrasound station is composed of an array of infrasound sensors capable of measuring micro-pressure changes produced at ground level by infrasonic waves. It is the responsibility of the Engineering and Development Section of the IMS Division to ensure the highest quality for IMS infrasound data. This includes the design of robust and reliable infrasound stations, the use of accurate and calibrated infrasound measuring chains, the installation of efficient wind noise reduction systems and the implementation of quality-control tools. The purpose of this paper is to present ongoing PTS infrasound engineering and development projects related to the testing and validation of wind noise reduction system models, the implementation of infrasound data QC tools, the definition of guidelines for the design of IMS power supply systems and the development of a portable infrasound calibrator and of field kits for site survey and certification.

  10. Automated infrasound signal detection algorithms implemented in MatSeis - Infra Tool.

    SciTech Connect

    Hart, Darren

    2004-07-01

    MatSeis's infrasound analysis tool, Infra Tool, uses frequency slowness processing to deconstruct the array data into three outputs per processing step: correlation, azimuth and slowness. Until now, an experienced analyst trained to recognize a pattern observed in outputs from signal processing manually accomplished infrasound signal detection. Our goal was to automate the process of infrasound signal detection. The critical aspect of infrasound signal detection is to identify consecutive processing steps where the azimuth is constant (flat) while the time-lag correlation of the windowed waveform is above background value. These two statements describe the arrival of a correlated set of wavefronts at an array. The Hough Transform and Inverse Slope methods are used to determine the representative slope for a specified number of azimuth data points. The representative slope is then used in conjunction with associated correlation value and azimuth data variance to determine if and when an infrasound signal was detected. A format for an infrasound signal detection output file is also proposed. The detection output file will list the processed array element names, followed by detection characteristics for each method. Each detection is supplied with a listing of frequency slowness processing characteristics: human time (YYYY/MM/DD HH:MM:SS.SSS), epochal time, correlation, fstat, azimuth (deg) and trace velocity (km/s). As an example, a ground truth event was processed using the four-element DLIAR infrasound array located in New Mexico. The event is known as the Watusi chemical explosion, which occurred on 2002/09/28 at 21:25:17 with an explosive yield of 38,000 lb TNT equivalent. Knowing the source and array location, the array-to-event distance was computed to be approximately 890 km. This test determined the station-to-event azimuth (281.8 and 282.1 degrees) to within 1.6 and 1.4 degrees for the Inverse Slope and Hough Transform detection algorithms, respectively, and

  11. Using large meteoroids as global infrasound reference events

    NASA Astrophysics Data System (ADS)

    Pilger, C.; Ceranna, L.; LE Pichon, A.; Brown, P.

    2015-12-01

    The explosive fragmentation of large meteoroids entering the Earth's atmosphere is one of the strongest sources of infrasonic waves and can be detected by infrasound arrays all over the world. Pressure perturbations of the strongest bolide events were detected at distances of thousands of kilometers, while for the 2013 Chelyabinsk superbolide, arrivals at long orthodrome distances (above 20000 km) and after complete circumnavigations of the globe (up to 87000 km) were recorded. Influence parameters on the detection capability of a single infrasound station on the one hand and of the complete global infrasound network of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) are investigated within this study and applied to a number of strong bolide events of the past 15 years. Potential influences on infrasound detection capability are due to the directivity of the acoustic source energy emission, the long-range ducting via stratosphere and thermosphere and the diurnal change of meteorological parameters and noise conditions at the stations during the signal arrivals. Since infrasound of large bolides has probably the most similar characteristics to an atmospheric nuclear explosion, it can be utilized as reference event for studies on the global performance of the International Monitoring System (IMS) of the CTBTO. Detections and non-detections of bolide infrasound at the more than 40 operational IMS infrasound stations are studied for the estimation of station and network performance and thus verification of nuclear test ban.

  12. Global Infrasound Monitoring of the Atmosphere

    NASA Astrophysics Data System (ADS)

    Bass, Henry

    2003-03-01

    As a signatory to the Comprehensive Nuclear Test Ban Treaty (CTBT), the United States has responsiblity for establishing and operating eight infrasound arrays from Alaska to the Antarctic through the Pacific Basin, and along the U. S. west coast. (In this context, infrasound is defined as acoustic waves in the frequency range 0.02 Hz to 4Hz.) In addition, the U. S. has non-CTBTO infrasound arrays in New Mexico, Utah, Nevada, Wyoming, Texas, and Maryland. The CTBT Office will install and operate an additional 52 states to provide worldwide coverage. This immense array of sensors provides a rare opportunity to study low frequency sound on a global scale. An international community of interested scieintists is beginning to emerge with different interests in the use of data from this global network. Much of the research interest lies in the ability to remotely monitor events of interest. These include volcanoes, severe storms, and bolides. The signals received at the individual stations are strongly dependent on the state of the intervening atmosphere therefore there is an opportunity to use tomography to gain more detailed knowledge of changes in the upper atmosphere. There are still great opportunities to improve the quality of the infrasound stations. Wind noise continues to limit the signal to noise level. Modern signal processing techniques might be used to lower wind noise levels and allow the detection of even weaker signals. Current generation infrasound stations are large and expensive. Reduction in complexity would allow a finer grid of stations and the study of higher frequency signals. There are numerous opportunities for collaborations in the use of this unique data source at the national and international levels. The US Infrasound Team and international collaborators are open to new ideas and colleagues.

  13. The Temporal Morphology of Infrasound Propagation

    NASA Astrophysics Data System (ADS)

    Drob, Douglas P.; Garcés, Milton; Hedlin, Michael; Brachet, Nicolas

    2010-05-01

    Expert knowledge suggests that the performance of automated infrasound event association and source location algorithms could be greatly improved by the ability to continually update station travel-time curves to properly account for the hourly, daily, and seasonal changes of the atmospheric state. With the goal of reducing false alarm rates and improving network detection capability we endeavor to develop, validate, and integrate this capability into infrasound processing operations at the International Data Centre of the Comprehensive Nuclear Test-Ban Treaty Organization. Numerous studies have demonstrated that incorporation of hybrid ground-to-space (G2S) enviromental specifications in numerical calculations of infrasound signal travel time and azimuth deviation yields significantly improved results over that of climatological atmospheric specifications, specifically for tropospheric and stratospheric modes. A robust infrastructure currently exists to generate hybrid G2S vector spherical harmonic coefficients, based on existing operational and emperical models on a real-time basis (every 3- to 6-hours) (D rob et al., 2003). Thus the next requirement in this endeavor is to refine numerical procedures to calculate infrasound propagation characteristics for robust automatic infrasound arrival identification and network detection, location, and characterization algorithms. We present results from a new code that integrates the local (range-independent) τp ray equations to provide travel time, range, turning point, and azimuth deviation for any location on the globe given a G2S vector spherical harmonic coefficient set. The code employs an accurate numerical technique capable of handling square-root singularities. We investigate the seasonal variability of propagation characteristics over a five-year time series for two different stations within the International Monitoring System with the aim of understanding the capabilities of current working knowledge of the

  14. Evaluation of Infrasound and Strobe Lights for Eliciting Avoidance Behavior in Juvenile Salmon and Char

    SciTech Connect

    Mueller, Robert P. ); Neitzel, Duane A. ); Amidan, Brett G. )

    2001-12-01

    Laboratory tests were conducted using juvenile chinook salmon Oncorhynchus tshawytscha, brook trout Salvelinus fontinalis, and rainbow trout O. mykiss to determine specific behavior responses to infrasound (< 20 Hz) and flashing strobe lights. The objective of these tests was to determine if juvenile salmonids could be deterred from entrainment at water diversion structures. Caged fish were acclimated in a static test tank and their behavior was recorded using low light cameras. Species-specific behavior was characterized by measuring movements of the fish within the cage and by observing startle and habituation responses. Wild chinook salmon (40-45 mm TL) and hatchery reared chinook salmon (45-50 mm TL) exhibited avoidance responses when initially exposed to a 10-Hz volume displacement source of infrasound. Rainbow and eastern brook trout (25-100 mm TL) did not respond with avoidance or other behaviors to infrasound. Evidence of habituation to the infrasound source was evident for chinook salmon during repeated exposures. Wild and hatchery chinook displayed a higher proportion of movement during the initial exposures to infrasound when the acclimation period in the test tank was 2-3 h as compared to a 12-15 h acclimation period. A flashing strobe light produced consistent movement in wild chinook salmon (60% of the tests), hatchery reared chinook salmon (50%), and rainbow trout (80%). No measurable responses were observed for brook trout. Results indicate that consistent, repeatable responses can be elicited from some fish using high-intensity strobe lights under a controlled laboratory testing. The species specific behaviors observed in these experiments might be used to predict how fish might react to low-frequency sound and strobe lights in a screening facility.

  15. The Eyjafjallajökull 2010 eruptions: Correlation study of volcanic tremor and infrasound

    NASA Astrophysics Data System (ADS)

    Jonsdottir, K.; Bean, C.; Vogfjord, K.; Ripepe, M.

    2012-04-01

    Volcanic far-field seismic tremor recorded at 7-20 km from the Eyjafjallajökull 2010 eruptions is investigated. Over a two months period, two very different eruptions occurred separated by 9 km and two days; an effusive flank eruption and later a highly explosive summit eruption. We observed high amplitude seismic tremor during the explosive eruption while the flank eruption produced very low amplitude tremor. Infrasound data collected for a few days during the summit eruption, as well as other data including plume height is also compared to the seismic tremor amplitude. We find that tremor amplitude does not scale with the plume height. However, in line with similar studies, the infrasound data, characterized by pressure pulses from the volcanic explosions, is seen to correlate temporally (0.55-0.6) with the seismic tremor data, characterized by repeating low frequency events. A high correlation in amplitude (0.8) is also found between these datasets. The analysis reveals a time lag of 15-20 seconds, where seismic low frequency events are seen prior to the infrasound events. This is consistent with co-located seismic tremor and infrasound sources at the eruptive crater, and a surface wave velocity of 1350-1500 m/s. Singlestation three component analyses (undertaken for several stations) of the seismic low frequency events further confirms that they contain Rayleigh wave energy.

  16. Contribution of the infrasound technology to characterize large scale atmospheric disturbances and impact on infrasound monitoring

    NASA Astrophysics Data System (ADS)

    Blanc, Elisabeth; Le Pichon, Alexis; Ceranna, Lars; Pilger, Christoph; Charlton Perez, Andrew; Smets, Pieter

    2016-04-01

    The International Monitoring System (IMS) developed for the verification of the Comprehensive nuclear-Test-Ban Treaty (CTBT) provides a unique global description of atmospheric disturbances generating infrasound such as extreme events (e.g. meteors, volcanoes, earthquakes, and severe weather) or human activity (e.g. explosions and supersonic airplanes). The analysis of the detected signals, recorded at global scales and over near 15 years at some stations, demonstrates that large-scale atmospheric disturbances strongly affect infrasound propagation. Their time scales vary from several tens of minutes to hours and days. Their effects are in average well resolved by the current model predictions; however, accurate spatial and temporal description is lacking in both weather and climate models. This study reviews recent results using the infrasound technology to characterize these large scale disturbances, including (i) wind fluctuations induced by gravity waves generating infrasound partial reflections and modifications of the infrasound waveguide, (ii) convection from thunderstorms and mountain waves generating gravity waves, (iii) stratospheric warming events which yield wind inversions in the stratosphere, (iv)planetary waves which control the global atmospheric circulation. Improved knowledge of these disturbances and assimilation in future models is an important objective of the ARISE (Atmospheric dynamics Research InfraStructure in Europe) project. This is essential in the context of the future verification of the CTBT as enhanced atmospheric models are necessary to assess the IMS network performance in higher resolution, reduce source location errors, and improve characterization methods.

  17. Dispersed Infrasound Signals in the "Zone of Silence"

    NASA Astrophysics Data System (ADS)

    Negraru, P.; Golden, P.; Herrin, E.

    2008-12-01

    During the last few years the use of seismo-acoustic recordings have become increasingly important; however, infrasound analysis methods lag behind seismic methods. The current paper discusses infrasonic signals in the so called 'Zone of Silence', at a distance up to 300 km from the source. During controlled source experiments in 2006 and 2007, tropospheric, stratospheric and thermospheric signals were recorded at a suite of temporary infrasound arrays; some of the tropospheric arrivals exhibit dispersion. The most common types of infrasonic signals observed during our studies beyond 76 km are stratospheric. These signals are not predicted by atmospheric modeling (raytracing and PE calculations) using the Naval Research Laboratory Ground to Space (G2S) model. The G2S model does not explain the observed tropospheric arrivals. Meteorological data from balloon launched rawinsondes obtained in the path of the propagating signals are able to predict the tropospheric propagation if the data closest to the detonation time is used. In a previous research study in the China Sea, a suite of dispersed infrasound signals were successfully interpreted as propagating in a low velocity waveguide. We also observed dispersed signals from an explosion at White Sands Missile Range recorded at TXIAR at a distance of 546 km. The signals exhibit dispersion between 0.2-1 Hz, and can be successfully modeled as propagating in a low velocity layer 1.2 km thick. However, dispersed signals recorded in Nevada suggest propagation in a waveguide consisting of a single low velocity layer is too simplistic. Effects due to lateral changes in effective sound speed, topography, turbulence and multiple layering can significantly affect the dispersion.

  18. Contribution of Infrasound to IDC Reviewed Event Bulletin

    NASA Astrophysics Data System (ADS)

    Bittner, Paulina; Polich, Paul; Gore, Jane; Ali, Sherif Mohamed; Medinskaya, Tatiana; Mialle, Pierrick

    2016-04-01

    Until 2003 two waveform technologies, i.e. seismic and hydroacoustic were used to detect and locate events included in the International Data Centre (IDC) Reviewed Event Bulletin (REB). The first atmospheric event was published in the REB in 2003 but infrasound detections could not be used by the Global Association (GA) Software due to the unmanageable high number of spurious associations. Offline improvements of the automatic processing took place to reduce the number of false detections to a reasonable level. In February 2010 the infrasound technology was reintroduced to the IDC operations and has contributed to both automatic and reviewed IDC bulletins. The primary contribution of infrasound technology is to detect atmospheric events. These events may also be observed at seismic stations, which will significantly improve event location. Examples of REB events, which were detected by the International Monitoring System (IMS) infrasound network were fireballs (e.g. Bangkok fireball, 2015), volcanic eruptions (e.g. Calbuco, Chile 2015) and large surface explosions (e.g. Tjanjin, China 2015). Query blasts and large earthquakes belong to events primarily recorded at seismic stations of the IMS network but often detected at the infrasound stations. Presence of infrasound detection associated to an event from a mining area indicates a surface explosion. Satellite imaging and a database of active mines can be used to confirm the origin of such events. This presentation will summarize the contribution of 6 years of infrasound data to IDC bulletins and provide examples of events recorded at the IMS infrasound network. Results of this study may help to improve location of small events with observations on infrasound stations.

  19. Detection and interpretation of seismoacoustic events at German infrasound stations

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Koch, Karl; Ceranna, Lars

    2016-04-01

    Three infrasound arrays with collocated or nearby installed seismometers are operated by the Federal Institute for Geosciences and Natural Resources (BGR) as the German National Data Center (NDC) for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Infrasound generated by seismoacoustic events is routinely detected at these infrasound arrays, but air-to-ground coupled acoustic waves occasionally show up in seismometer recordings as well. Different natural and artificial sources like meteoroids as well as industrial and mining activity generate infrasonic signatures that are simultaneously detected at microbarometers and seismometers. Furthermore, many near-surface sources like earthquakes and explosions generate both seismic and infrasonic waves that can be detected successively with both technologies. The combined interpretation of seismic and acoustic signatures provides additional information about the origin time and location of remote infrasound events or about the characterization of seismic events distinguishing man-made and natural origins. Furthermore, seismoacoustic studies help to improve the modelling of infrasound propagation and ducting in the atmosphere and allow quantifying the portion of energy coupled into ground and into air by seismoacoustic sources. An overview of different seismoacoustic sources and their detection by German infrasound stations as well as some conclusions on the benefit of a combined seismoacoustic analysis are presented within this study.

  20. Monitoring the Earth's Atmosphere with the Global IMS Infrasound Network

    NASA Astrophysics Data System (ADS)

    Brachet, Nicolas; Brown, David; Mialle, Pierrick; Le Bras, Ronan; Coyne, John; Given, Jeffrey

    2010-05-01

    , they represent valuable data for other civil applications like monitoring of natural hazards (volcanic activity, storm tracking) and climate change. Non-noise detections are used in network processing at the IDC along with seismic and hydroacoustic technologies. The arrival phases detected on the three waveform technologies may be combined and used for locating events in an automatically generated bulletin of events. This automatic event bulletin is routinely reviewed by analysts during the interactive review process. However, the fusion of infrasound data with the other waveform technologies has only recently (in early 2010) become part of the IDC operational system, after a software development and testing period that began in 2004. The build-up of the IMS infrasound network, the recent developments of the IDC infrasound software, and the progress accomplished during the last decade in the domain of real-time atmospheric modelling have allowed better understanding of infrasound signals and identification of a growing data set of ground-truth sources. These infragenic sources originate from natural or man-made sources. Some of the detected signals are emitted by local or regional phenomena recorded by a single IMS infrasound station: man-made cultural activity, wind farms, aircraft, artillery exercises, ocean surf, thunderstorms, rumbling volcanoes, iceberg calving, aurora, avalanches. Other signals may be recorded by several IMS infrasound stations at larger distances: ocean swell, sonic booms, and mountain associated waves. Only a small fraction of events meet the event definition criteria considering the Treaty verification mission of the Organization. Candidate event types for the IDC Reviewed Event Bulletin include atmospheric or surface explosions, meteor explosions, rocket launches, signals from large earthquakes and explosive volcanic eruptions.

  1. Antarctic Atmospheric Infrasound.

    DTIC Science & Technology

    1981-11-30

    A summary is given of the project chronology and the reports describing our research in Antarctic Atmospheric infrasound. Analysis of selected infrasonic signals is discussed and a list is given of all infrasonic waves received on the digital system with correlation coefficient greater than 0.6. (Author)

  2. Infrasound absorption by atmospheric clouds

    NASA Astrophysics Data System (ADS)

    Baudoin, Michael; Coulouvrat, Francois; Thomas, Jean-Louis

    2010-05-01

    A model is developed for the absorption of infrasound by atmospheric clouds made of a suspension of liquid water droplets within a gaseous mixture of water vapor and air. The model is based on the work of D.A. Gubaidullin and R.I. Nigmatulin [Int. J. Multiphase Flow, 26, 207-228, 2000], which is applied to atmospheric clouds. Three physical mechanisms are included : unsteady viscous drag associated with momentum transfers due to the translation of water droplets, unsteady thermal transfers between the liquid and gaseous phases, and mass transfers due to the evaporation or condensation of the water phase. For clouds, in the infrasonic frequency range, phase changes are the dominant mechanisms (around 1 Hz), while viscous and heat transfers become significant only around 100 Hz. Mass transfers involve two physical effects : evaporation and condensation of the water phase at the droplet surface, and diffusion of the water vapor within the gaseous phase. The first one is described through the Hertz-Knudsen-Langmuir theory based on kinetic theory. It involves a little known coefficient known as coefficient of accommodation. The second one is the classical Fick diffusion. For clouds, and unless the coefficient of accommodation is very small (far from the generally recommended value is close to one), diffusion is the main limiting effects for mass transfers. In a second stage, the sound and infrasound absorption is evaluated for various typical clouds up to about 4 km altitude. Above this altitude, the ice content of clouds is dominant compared to their water content, and the present model is not applicable. Cloud thickness, water content, and droplets size distribution are shown to be the major factors influencing the infrasound absorption. A variety of clouds have been analyzed. In most cases, it is shown that infrasound absorption within clouds is several orders larger than classical absorption (due to molecular relaxation of nitrogen and oxygen molecules in presence

  3. Nonlinear synthesis of infrasound propagation through an inhomogeneous, absorbing atmosphere.

    PubMed

    de Groot-Hedlin, C D

    2012-08-01

    An accurate and efficient method to predict infrasound amplitudes from large explosions in the atmosphere is required for diverse source types, including bolides, volcanic eruptions, and nuclear and chemical explosions. A finite-difference, time-domain approach is developed to solve a set of nonlinear fluid dynamic equations for total pressure, temperature, and density fields rather than acoustic perturbations. Three key features for the purpose of synthesizing nonlinear infrasound propagation in realistic media are that it includes gravitational terms, it allows for acoustic absorption, including molecular vibration losses at frequencies well below the molecular vibration frequencies, and the environmental models are constrained to have axial symmetry, allowing a three-dimensional simulation to be reduced to two dimensions. Numerical experiments are performed to assess the algorithm's accuracy and the effect of source amplitudes and atmospheric variability on infrasound waveforms and shock formation. Results show that infrasound waveforms steepen and their associated spectra are shifted to higher frequencies for nonlinear sources, leading to enhanced infrasound attenuation. Results also indicate that nonlinear infrasound amplitudes depend strongly on atmospheric temperature and pressure variations. The solution for total field variables and insertion of gravitational terms also allows for the computation of other disturbances generated by explosions, including gravity waves.

  4. Infrasound ray tracing models for real events

    NASA Astrophysics Data System (ADS)

    Averbuch, Gil; Applbaum, David; Price, Colin; Ben Horin, Yochai

    2015-04-01

    's height or the sprite's most energetic part. Even though atmospheric wind has a strong influence on infrasound wave propagation, our estimation is that for high altitude sources, extreme weather in the troposphere below has low impact on the trajectories of the waves.

  5. Study of the wind velocity-layered structure in the stratosphere, mesosphere, and lower thermosphere by using infrasound probing of the atmosphere

    NASA Astrophysics Data System (ADS)

    Chunchuzov, I.; Kulichkov, S.; Perepelkin, V.; Popov, O.; Firstov, P.; Assink, J. D.; Marchetti, E.

    2015-09-01

    The wind velocity structure in the upper stratosphere, mesosphere, and lower thermosphere (MLT) is studied with the recently developed method of infrasound probing of the atmosphere. The method is based on the effect of infrasound scattering from highly anisotropic wind velocity and temperature inhomogeneities in the middle and upper atmosphere. The scattered infrasound field propagates in the acoustic shadow zones, where it is detected by microbarometers. The vertical profiles of the wind velocity fluctuations in the upper stratosphere (30-52 km) and MLT (90-140 km) are retrieved from the waveforms and travel times of the infrasound signals generated by explosive sources such as volcanoes and surface explosions. The fine-scale wind-layered structure in these layers was poorly observed until present time by other remote sensing methods, including radars and satellites. It is found that the MLT atmospheric layer (90-102 km) can contain extremely high vertical gradients of the wind velocity, up to 10 m/s per 100 m. The effect of a fine-scale wind velocity structure on the waveforms of infrasound signals is studied. The vertical wave number spectra of the retrieved wind velocity fluctuations are obtained for the upper stratosphere. Despite the difference in the locations of the explosive sources all the obtained spectra show the existence of high vertical wave number spectral tail with a -3 power law decay. The obtained spectral characteristics of the wind fluctuations are necessary for improvement of gravity wave drag parameterizations for numerical weather forecast.

  6. Incorporating numerical modelling into estimates of the detection capability of the IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Ceranna, L.

    2011-12-01

    To monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), a dedicated International Monitoring System (IMS) is being deployed. Recent global scale observations recorded by this network confirm that its detection capability is highly variable in space and time. Previous studies estimated the radiated source energy from remote observations using empirical yield-scaling relations which account for the along-path stratospheric winds. Although the empirical wind correction reduces the variance in the explosive energy versus pressure relationship, strong variability remains in the yield estimate. Today, numerical modelling techniques provide a basis to better understand the role of different factors describing the source and the atmosphere that influence propagation predictions. In this study, the effects of the source frequency and the stratospheric wind speed are simulated. In order to characterize fine-scale atmospheric structures which are excluded from the current atmospheric specifications, model predictions are further enhanced by the addition of perturbation terms. Thus, a theoretical attenuation relation is developed from massive numerical simulations using the Parabolic Equation method. Compared with previous studies, our approach provides a more realistic physical description of infrasound propagation. We obtain a new relation combining a near-field and far-field term which account for the effects of both geometrical spreading and dissipation on the pressure wave attenuation. By incorporating real ambient infrasound noise at the receivers which significantly limits the ability to detect and identify signals of interest, the minimum detectable source amplitude can be derived in a broad frequency range. Empirical relations between the source spectrum and the yield of explosions are used to infer detection thresholds in tons of TNT equivalent. In the context of the future verification of the CTBT, the obtained attenuation relation quantifies

  7. Infrasound monitoring, acoustic-gravity waves and global atmospheric dynamics

    NASA Astrophysics Data System (ADS)

    Blanc, E.; Le Pichon, A.; Ceranna, L.; Farges, T.

    2008-12-01

    For the verification of the Comprehensive nuclear Test Ban Treaty, the International Monitoring System has been developed. As part of this system, the infrasound network provides an unique opportunity to monitor continuously pressure waves in the atmosphere. Such infrasonic waves propagate in the channel formed by the temperature and wind gradients of the atmosphere. Long term observations provide information about the evolution of the propagation conditions and then of atmospheric parameters. The monitoring of continuous sources, as ocean swell, gives the characteristics of the stratospheric wave channel submitted to stratospheric warming effects. Large scale gravity waves, which are also observed by the network, produce a forcing of the stratosphere at low and middle latitudes and long-lived changes in the stratospheric circulation towards high latitudes, leading to fluctuations in the strength of the polar vortex. These fluctuations move down to the lower stratosphere with possible effects on the tropospheric temperature. Gravity wave monitoring in Antarctica reveals a gravity wave system probably related to the wind effect over mountains. At mid latitudes an additional main sources of disturbances is the thunderstorm activity. The infrasound monitoring system allows a better knowledge of the atmospheric wave systems and of the dynamics of the atmosphere. In return this better knowledge of the wave systems allow a better identification of the possible explosion signals in the background of the atmospheric waves and then to improve the discrimination methods

  8. Antarctic Atmospheric Infrasound.

    DTIC Science & Technology

    1986-11-01

    system. These are microbaroms, aurural infrasonic waves, mountain associated infrasound, Mount Erebus eruptive events, and signals related to large...array. Mount Erebus is an active volcano located only fifteen miles from the Windless Bight array. Frequent mini-eruptions from the lava lake at the...MAX, Velocity MIN & MAX, and Start & Stop. To produce a listing of all events that were caused by Mount Erebus on the tape: Choose the T array, and

  9. BBN technical memorandum W1291 infrasound model feasibility study

    SciTech Connect

    Farrell, T., BBN Systems and Technologies

    1998-05-01

    The purpose of this study is to determine the need and level of effort required to add existing atmospheric databases and infrasound propagation models to the DOE`s Hydroacoustic Coverage Assessment Model (HydroCAM) [1,2]. The rationale for the study is that the performance of the infrasound monitoring network will be an important factor for both the International Monitoring System (IMS) and US national monitoring capability. Many of the technical issues affecting the design and performance of the infrasound network are directly related to the variability of the atmosphere and the corresponding uncertainties in infrasound propagation. It is clear that the study of these issues will be enhanced by the availability of software tools for easy manipulation and interfacing of various atmospheric databases and infrasound propagation models. In addition, since there are many similarities between propagation in the oceans and in the atmosphere, it is anticipated that much of the software infrastructure developed for hydroacoustic database manipulation and propagation modeling in HydroCAM will be directly extendible to an infrasound capability. The study approach was to talk to the acknowledged domain experts in the infrasound monitoring area to determine: 1. The major technical issues affecting infrasound monitoring network performance. 2. The need for an atmospheric database/infrasound propagation modeling capability similar to HydroCAM. 3. The state of existing infrasound propagation codes and atmospheric databases. 4. A recommended approach for developing the required capabilities. A list of the people who contributed information to this study is provided in Table 1. We also relied on our knowledge of oceanographic and meteorological data sources to determine the availability of atmospheric databases and the feasibility of incorporating this information into the existing HydroCAM geographic database software. This report presents a summary of the need for an integrated

  10. Sayarim Infrasound Calibration Explosion provides first GT0 dataset for CTBTO

    NASA Astrophysics Data System (ADS)

    Gitterman, Yefim

    2010-05-01

    The large-scale calibration explosion of about 82 tons of HE explosives, assembled as a pyramid on the soft sediment surface, was successfully conducted by the Geophysical Institute of Israel at Sayarim Military Range on 26 August 2009. High-pressure values, measured in the range 200-600 m, were higher than predicted, whereas the created crater and seismic magnitude were smaller than expected for this on-surface charge. These results confirm that the used explosives, charge design and upward detonation provided the necessary explosion energy generation and partition: maximum of energy to the atmosphere and minimum to the ground. The high-pressure observations were utilized for estimation of the important Ground Truth parameter - TNT equivalent yield of about 0.1 kT (based on positive impulse in air-shock wave). Thus the Sayarim Explosion provided the first full GT0 source dataset for on-surface large-scale explosions, recorded by infrasound stations of International Monitoring System (IMS). Infrasound signals were well observed at distances up to 3,500 km, at numerous portable and permanent stations in Israel, Mediterranean countries and north-central Europe, including two IMS stations I26DE and I48TN and two portable arrays in Austria and Northern Italy deployed by the CTBTO team. Obtained records were used for analysis of infrasound signal propagation, source location and yield estimation, and comparison with GT0 source parameters.

  11. Capability of the CTBT infrasound stations detecting the 2013 Russian fireball

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars; Ross, J. Ole; Le Pichon, Alexis; Mialle, Pierrick; Garces, Milton

    2015-04-01

    The explosive fragmentation of the 2013 Chelyabinsk meteorite generated a large airburst with an equivalent yield of 500 kT TNT. It is the most energetic event recorded by the infrasound component of the CTBT-IMS, globally detected by 20 out of 42 operational stations. This study performs a station-by-station estimation of the IMS detection capability to explain infrasound detections and non-detections from short to long distances, using the Chelyabinsk meteorite as global reference event. Investigated parameters influencing the detection capability are the directivity of the line source signal, the ducting of acoustic energy and the individual noise conditions at each station. Findings include a clear detection preference for stations perpendicular to the meteorite trajectory, even over large distances. Only a weak influence of stratospheric ducting is observed for this low-frequency case. Furthermore, a strong dependence on the diurnal variability of background noise levels at each station is observed, favoring nocturnal detections.

  12. Inferring atmospheric weather conditions in volcanic environments using infrasound

    NASA Astrophysics Data System (ADS)

    Ortiz, H. D.; Johnson, J. B.; Ruiz, M. C.

    2015-12-01

    We use infrasound produced by Tungurahua Volcano (Ecuador) to infer local time-varying atmospheric conditions, which can be used to improve gas flux measurements and tephra dispersal modeling. Physical properties of the atmosphere, including wind and temperature (which controls adiabatic sound speed), can be quantified by studying the travel times of acoustic waves produced during volcanic activity. The travel times between Tungurahua's vent and five infrasound stations located in a network configuration over an area of 90 km2 were used in this study. We are able to quantify the arrival time differences of acoustic waves for ten unique station pairs and use this information to model the average speed of sound between source and receiver. To identify what parameters best fit the observed arrival times, we perform a grid search for a homogeneous two-dimensional wind velocity as well as for air temperature. Due to travel time dependence on the specific path taken by waves, we account for topography using a 5 meter resolution digital elevation model of Tungurahua. To investigate the time-varying atmospheric structure we use data recorded at Tungurahua volcano, during a strombolian eruptive phase in August 2012, however the methodology can be applied to continuous network infrasound data collected since July 2006 as part of the Japanese-Ecuadorian Cooperation Project: "Enhancement of the Volcano Monitoring Capacity in Ecuador". We propose that the computation of wind velocities will help to improve gas flux measurements that are based on remote sensing techniques like Differential Optical Absorption Spectroscopy (DOAS), resulting in better estimates of sulfur fluxes that can then be related to magma fluxing into the volcanic system. Further, wind field quantification close to the volcano can improve numerical models that are used to forecast tephra deposits, thereby helping to mitigate their effect on inhabitants, infrastructure, livestock, and crops.

  13. Infrasound from lightning: characteristics and impact on an infrasound station

    NASA Astrophysics Data System (ADS)

    Farges, T.; Blanc, E.

    2009-12-01

    More than two third of the infrasound stations of the International Monitoring System (IMS) of the CTBTO are now certified and measure routinely signals due particularly to natural activity (swell, volcano, severe weather including lightning, …). It is well established that more than 2,000 thunderstorms are continuously active all around the world and that about 45 lightning flashes are produced per second over the globe. During the Eurosprite 2005 campaign, we took the opportunity to measure, in France during summer, infrasound from lightning and from sprites (which are transient luminous events occurring over thunderstorm). We examine the possibility to measure infrasound from lightning when thunderstorms are close or far from the infrasound station. Main results concern detection range of infrasound from lightning, amplitude vs. distance law, and characteristics of frequency spectrum. We show clearly that infrasound from lightning can be detected when the thunderstorm is within about 75 km from the station. In good noise conditions, infrasound from lightning can be detected when thunderstorms are located more than 200 km from the station. No signal is recorded from lightning flashes occurring between 75 and 200 km away from the station, defining then a silence zone. When the thunderstorm is close to the station, the infrasound signal could reach several Pascal. The signal is then on average 30 dB over the noise level at 1 Hz. Infrasound propagate upward where the highest frequencies are dissipated and can produce a significant heating of the upper mesosphere. Some of these results have been confirmed by case studies with data from the IMS Ivory Coast station. The coverage of the IMS stations is very good to study the thunderstorm activity and its disparity which is a good proxy of the global warming. Progress in data processing for infrasound data in the last ten years and the appearance of global lightning detection network as the World Wide Lightning

  14. Infrasound from lightning: characteristics and impact on an infrasound station

    NASA Astrophysics Data System (ADS)

    Farges, Thomas; Blanc, Elisabeth

    2010-05-01

    More than two third of the infrasound stations of the International Monitoring System (IMS) of the CTBTO are now certified and measure routinely signals due particularly to natural activity (swell, volcano, severe weather including lightning, …). It is well established that more than 2,000 thunderstorms are continuously active all around the world and that about 45 lightning flashes are produced per second over the globe. During the Eurosprite 2005 campaign, we took the opportunity to measure, in France during summer, infrasound from lightning and from sprites (which are transient luminous events occurring over thunderstorm). We examine the possibility to measure infrasound from lightning when thunderstorms are close or far from the infrasound station. Main results concern detection range of infrasound from lightning, amplitude vs. distance law, and characteristics of frequency spectrum. We show clearly that infrasound from lightning can be detected when the thunderstorm is within about 75 km from the station. In good noise conditions, infrasound from lightning can be detected when thunderstorms are located more than 200 km from the station. No signal is recorded from lightning flashes occurring between 75 and 200 km away from the station, defining then a silence zone. When the thunderstorm is close to the station, the infrasound signal could reach several Pascal. The signal is then on average 30 dB over the noise level at 1 Hz. Infrasound propagate upward where the highest frequencies are dissipated and can produce a significant heating of the upper mesosphere. Some of these results have been confirmed by case studies with data from the IMS Ivory Coast station. The coverage of the IMS stations is very good to study the thunderstorm activity and its disparity which is a good proxy of the global warming. Progress in data processing for infrasound data in the last ten years and the appearance of global lightning detection network as the World Wide Lightning

  15. IDC infrasound analysis of the 15 February 2013 Chelyabinsk fireball

    NASA Astrophysics Data System (ADS)

    Mialle, P.; Bittner, P.; Brown, D.; Polich, P.; Gore, J.

    2013-12-01

    The first atmospheric event built only from infrasound arrivals was reported in the Reviewed Event Bulletin (REB) of the International Data Centre (IDC) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) in 2003. In the last decade, 45 infrasound stations from the International Monitoring System (IMS) have been installed and are transmitting data to the IDC. In early 2010 the IDC began routine automatic processing of infrasound data reviewed by interactive analysis; the detected and located events are now systematically included in the REB. This study focuses on a major infragenic event that occurred in February 2013 and was thoroughly analyzed at the IDC. On February 15 a fireball in the Chelyabinsk region (Russia) was observed generating infrasound waves that were recorded by 20 infrasound IMS stations globally spread from Greenland to Antarctica. Chronology of the analysis and specificities of this event will be introduced. This event is the largest ever recorded by the infrasound component of the IMS network. Related seismic observations were also found.

  16. USGS VDP Infrasound Sensor Evaluation

    SciTech Connect

    Slad, George William; Merchant, Bion J.

    2016-10-01

    Sandia National Laboratories has tested and evaluated two infrasound sensors, the model VDP100 and VDP250, built in-house at the USGS Cascades Volcano Observatory. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, self-noise, dynamic range and nominal transfer function. Notable features of the VDP sensors include novel and durable construction and compact size.

  17. Experimental Infrasound Studies in Nevada

    NASA Astrophysics Data System (ADS)

    Herrin, E. T.; Negraru, P. T.; Golden, P.; Williams, A.

    2009-12-01

    An experimental propagation study was carried out in Nevada in June 2009 on Julian days 173-177. During this field experiment we deployed 16 single channel digital infrasound recorders to monitor the munitions disposal activities near Hawthorne, NV. The sensors were deployed in a single line and placed approximately 12 km apart at distances ranging from 2 to 177 km. A four element semi-permanent infrasound array named FNIAR was installed approximately 154 km north of the detonation site in line with the individual temporary recorders. Tropospheric arrivals were observed during all days of the experiment, but during day 176 the observed arrivals had very large amplitudes. A large signal was observed at 58 km from the detonation site with amplitude as large as 4 Pascals, while at 94 km no signal was observed. At FNIAR the amplitude of the tropospheric arrival was 1 Pascal. During this day meteorological data acquired in the propagation path showed a strong jet stream to the north. On day 177 we were not able to identify tropospheric arrivals beyond 34 km, but at stations beyond 152 km we observed stratospheric arrivals. Continuous monitoring of these signals at FNIAR shows that stratospheric arrivals are the most numerous. In a two month period, from 06/15/2009 to 08/15/2009 there were 35 operational days at the Hawthorne disposal facility resulting in 212 explosions with known origin times. Based on the celerity values there were 115 explosions that have only stratospheric arrivals (celerities of 300-275 m/s), 72 explosions with both tropospheric (celerities above 330 m/s) and stratospheric arrivals, 20 explosions that were not detected and five explosions that have only tropospheric arrivals.

  18. Evaluation of Infrasound and Strobe Lights to Elicit Avoidance Behavior in Juvenile Salmon and Char.

    SciTech Connect

    Mueller, Robert, P.; Neitzel, Duane A.; Amidan, Brett G.

    1999-02-01

    Experimental tests were conducted using hatchery reared and wild juvenile chinook salmon Oncorhynchus tshawytscha, eastern brook trout Salvelinus fontinalis, and rainbow trout O. mykiss to determine specific behavior responses to infrasound (<20 Hz) and flashing strobe lights. Caged fish were acclimated in a static test tank and their behavior was recorded using low light cameras. Species specific behavior was characterized by measuring movements of the fish within the cage as well as observing startle and habituation responses. Wild chinook salmon (40-45 mm) and hatchery reared chinook salmon (45-50mm) exhibited avoidance responses when initially exposed to a 10 Hz volume displacement source. Rainbow and eastern brook trout (25-100 mm) did not respond with avoidance or other behaviors to infrasound. Habituation to the infrasound source was evident for chinook salmon during repeated exposures. Wild and hatchery chinook displayed a higher proportion of movement during the initial exposures to infrasound when the acclimation period in the test tank was 2-3 h as compared to a 12-15 h acclimation period. A flashing strobe light produced higher and more consistent movement rates in wild chinook (60% of the tests); hatchery reared chinook salmon (50%) and rainbow trout (80%). No measurable movement or other responses was observed for eastern brook trout. Little if any habituation was observed during repeated exposures to strobe lights. Results from this study indicate that consistent repeatable responses can be elicited from some fish using high intensity strobe lights under a controlled laboratory testing. The specific behaviors observed in these experiments might be used to predict how fish might react to low frequency sound and strobe lights in a screening facility. Because sub-yearling salmonids and resident species are susceptible from becoming entrained at water diversion structures we conducted tests in conjunction with our evaluation of juvenile fish screening

  19. Sayarim Infrasound Calibration Explosion: Near-Source and Local Observations and Yield Estimation

    DTIC Science & Technology

    2010-09-01

    of large-scale explosions on soft soil (Adushkin and Khristoforov , 2004): R = 3.36W0.336; H = 1.78W0.316 , (1) where W is TNT equivalent... Khristoforov (2004). Craters of large-scale surface explosions, Combust, Explo. Shock Waves 40: 674–678. Bowman, J. R., H. Israelsson, G. Shields, M

  20. Characterizing complex eruptive activity at Santiaguito, Guatemala using infrasound semblance in networked arrays

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Lees, J.; Varley, N.

    2011-01-01

    We implement an infrasound semblance technique to identify acoustic sources originating from volcanic vents and apply the technique to the generally low-amplitude infrasound (< 3 Pa at 1 km) signals produced by Santiaguito dome in Guatemala. Semblance detection is demonstrated with data collected from two-element miniature arrays with ~ 30 m spacing between elements. The semblance technique is effective at identifying a range of eruptive phenomena, including pyroclastic-laden eruptions, vigorous degassing events, and rockfalls, even during periods of high wind contamination Many of the detected events are low in amplitude (tens of mPa) such that they are observed only by select arrays positioned with proximity and line-of-sight to the source. Larger events, such as the pyroclastic-laden eruptions, which occurred bi-hourly in 2009, were detected by all five arrays and produced an infrasonic signal that was correlated across the network. Network correlated events can be roughly located and map to the summit of the Caliente Vent where pyroclastic-laden eruptions originate. In general, the degree of Santiaguito infrasound event correlation is poor across the network, suggesting that complex source geometry contributes to asymmetric sound radiation.

  1. Infrasounds and biorhythms of the human brain

    NASA Astrophysics Data System (ADS)

    Panuszka, Ryszard; Damijan, Zbigniew; Kasprzak, Cezary; McGlothlin, James

    2002-05-01

    Low Frequency Noise (LFN) and infrasound has begun a new public health hazard. Evaluations of annoyance of (LFN) on human occupational health were based on standards where reactions of human auditory system and vibrations of parts of human body were small. Significant sensitivity has been observed on the central nervous system from infrasonic waves especially below 10 Hz. Observed follow-up effects in the brain gives incentive to study the relationship between parameters of waves and reactions obtained of biorhythms (EEG) and heart action (EKG). New results show the impact of LFN on the electrical potentials of the brain are dependent on the pressure waves on the human body. Electrical activity of circulatory system was also affected. Signals recorded in industrial workplaces were duplicated by loudspeakers and used to record data from a typical LFN spectra with 5 and 7 Hz in a laboratory chamber. External noise, electromagnetic fields, temperature, dust, and other elements were controlled. Results show not only a follow-up effect in the brain but also a result similar to arrhythmia in the heart. Relaxations effects were observed of people impacted by waves generated from natural sources such as streams and waterfalls.

  2. The case for infrasound as the long-range map cue in avian navigation

    USGS Publications Warehouse

    Hagstrum, J.T.

    2007-01-01

    Of the various 'map' and 'compass' components of Kramer's avian navigational model, the long-range map component is the least well understood. In this paper atmospheric infrasounds are proposed as the elusive longrange cues constituting the avian navigational map. Although infrasounds were considered a viable candidate for the avian map in the 1970s, and pigeons in the laboratory were found to detect sounds at surprisingly low frequencies (0.05 Hz), other tests appeared to support either of the currently favored olfactory or magnetic maps. Neither of these hypotheses, however, is able to explain the full set of observations, and the field has been at an impasse for several decades. To begin, brief descriptions of infrasonic waves and their passage through the atmosphere are given, followed by accounts of previously unexplained release results. These examples include 'release-site biases' which are deviations of departing pigeons from the homeward bearing, an annual variation in homing performance observed only in Europe, difficulties orienting over lakes and above temperature inversions, and the mysterious disruption of several pigeon races. All of these irregularities can be consistently explained by the deflection or masking of infrasonic cues by atmospheric conditions or by other infrasonic sources (microbaroms, sonic booms), respectively. A source of continuous geographic infrasound generated by atmosphere-coupled microseisms is also proposed. In conclusion, several suggestions are made toward resolving some of the conflicting experimental data with the pigeons' possible use of infrasonic cues.

  3. Nonlinear Propagation of Infrasound from Large Explosions

    NASA Astrophysics Data System (ADS)

    de Groot-Hedlin, Catherine

    2015-04-01

    Atmospheric explosions release immense quantities of infrasound energy that can be detected at receivers located from hundreds to thousands of kilometers from the origin. This has led to the deployment of a global 60-station network of micro-barometer arrays to aid in nuclear explosion monitoring. Current methods of estimating the radiated source energy from remote recordings of infrasound signals use simplified empirical source-yield relations that account for stratospheric winds along the source-receiver path. These formulations apply only to direct and stratospherically ducted arrivals. More recently, considerable progress has been made in applying numerical modeling techniques to develop more accurate source-yield formulations for realistic sound and wind speed profiles. However, these methods assume linear infrasound propagation along the travel path even though nonlinear effects - which arise when the amplitude of the acoustic pressure perturbation is a finite fraction of the ambient atmospheric pressure - are known to significantly alter infrasound frequencies, velocities and amplitudes, and thus can affect derived source yield estimates. For realistic atmospheric profiles, nonlinearity can be significant both in the vicinity of a large explosive source as well as at much greater distances. Within the stratosphere, nonlinearity may arise at caustics created by ducting; in the thermosphere, nonlinearity may arise due to very low ambient pressures at high altitudes. In this study, the effects of nonlinearity on infrasound signal amplitudes and frequencies are simulated using a nonlinear finite difference, time-domain (FDTD) method. The key features that allow for accurate and efficient nonlinear synthesis of infrasound propagation through realistic media are that 1) it includes for atmospheric viscosity, and 2) the environmental models are constrained to have axial symmetry, yielding solutions relevant to a point source in a fully 3D model with rotational

  4. Infrasound detections of polar lows during the last three winters from the Norwegian infrasound station #IS18.

    NASA Astrophysics Data System (ADS)

    Pol, Katy; Claud, Chantal; Rojo, Maxence; Le Pichon, Alexis; Hauchecorne, Alain; Blanc, Elisabeth

    2017-04-01

    Polar lows are intense and very short (1 or 2 days) high latitude maritime cyclones of small horizontal (few hundred kilometers) and vertical scales (up to 5 km), that develop when very cold air is advected over relatively warmer water. Associated with severe meteorological conditions (large ocean waves, heavy precipitations, thunders and low visibility), they represent a real hazard for maritime and coastal activities but remain difficult to forecast, because of their rarity and the scarcity of observations in polar regions where they develop. With the signature of the Comprehensive Nuclear-Test-Ban Treaty (CTBT - http://www.ctbto.org) in 1996, a global infrasound monitoring network (named International Monitoring System - IMS) has been developed and provides a potential new technology to detect polar lows. According to Orbaek and Naustvik (1995), polar lows are indeed assumed to generate strong infrasound signals in the frequency range of 0.2-13 Hz, which are detectable over distances of up to 1000km. However, until recently and the exploratory study of Claud et al. (submitted), no similar study was available to generalize the possibility to use infrasound, as an alternative technology to detect and monitor polar lows. By analysing the infrasound measurements of the Norwegian infrasound station #IS18, we here try to detect the infrasound signatures of dated polar lows in the Barents and Norwegian Seas, during the 2013-2014, 2014-2015 and 2015-2016 winters.

  5. Overview of the 2009 and 2011 Sayarim Infrasound Calibration Experiments

    NASA Astrophysics Data System (ADS)

    Fee, David; Waxler, Roger; Assink, Jelle; Gitterman, Yefim; Given, Jeffrey; Coyne, John; Mialle, Pierrick; Garces, Milton; Drob, Douglas; Kleinert, Dan; Hofstetter, Rami; Grenard, Patrick

    2013-06-01

    Three large-scale infrasound calibration experiments were conducted in 2009 and 2011 to test the International Monitoring System (IMS) infrasound network and provide ground truth data for infrasound propagation studies. Here we provide an overview of the deployment, detonation, atmospheric specifications, infrasound array observations, and propagation modeling for the experiments. The experiments at the Sayarim Military Range, Israel, had equivalent TNT yields of 96.0, 7.4, and 76.8 t of explosives on 26 August 2009, 24 January 2011, and 26 January 2011, respectively. Successful international collaboration resulted in the deployment of numerous portable infrasound arrays in the region to supplement the IMS network and increase station density. Infrasound from the detonations is detected out to ~3500 km to the northwest in 2009 and ~6300 km to the northeast in 2011, reflecting the highly anisotropic nature of long-range infrasound propagation. For 2009, the moderately strong stratospheric wind jet results in a well-predicted set of arrivals at numerous arrays to the west-northwest. A second set of arrivals is also apparent, with low celerities and high frequencies. These arrivals are not predicted by the propagation modeling and result from unresolved atmospheric features. Strong eastward tropospheric winds (up to ~70 m/s) in 2011 produce high-amplitude tropospheric arrivals recorded out to >1000 km to the east. Significant eastward stratospheric winds (up to ~80 m/s) in 2011 generate numerous stratospheric arrivals and permit the long-range detection (i.e., >1000 km). No detections are made in directions opposite the tropospheric and stratospheric wind jets for any of the explosions. Comparison of predicted transmission loss and observed infrasound arrivals gives qualitative agreement. Propagation modeling for the 2011 experiments predicts lower transmission loss in the direction of the downwind propagation compared to the 2009 experiment, consistent with the

  6. Comparison of seismic and infrasound wave fields generated by snow avalanches

    NASA Astrophysics Data System (ADS)

    Suriñach, Emma; Tapia, Mar; Pérez-Guillén, Cristina; Khazaradze, Giorgi; Roig, Pere

    2016-04-01

    Snow avalanches are a source of waves that are transmitted through the ground and the air. These wave fields are detected by seismic and infrasound sensors. During the winter seasons 2008 -2016, a good quality database of avalanches was obtained at the VdlS test site with an accurate instrumentation. These avalanches were both natural and artificially triggered and were of varying types and sizes. Distances involved were 0.5 -3 km. Seismic signals were acquired using three seismometers (3-components, 1Hz) spaced 600 m apart along the avalanche track. One infrasound sensor (0.1Hz) and one seismometer (3-components, 1Hz) were placed one next to the other with a common base of time on the slope opposite the path. The database obtained enables us to compare the different signals generated. Differences in the frequency content and shape of the signals depending on the type and size of the avalanche are detected. A clear evolution of the recorded seismic signals along the path is observed. The cross correlation of the infrasound and seismic signals generated by the avalanches allows us to determine different characteristics for powder, transitional and wet avalanches concerning their wave fields. The joint analysis of infrasound and seismic waves enables us to obtain valuable information about the internal parts of the avalanche as a source of each wave field. This study has repercussions on avalanche dynamics and on the selection of the appropriate avalanche detection system. This study is supported by the Spanish Ministry of Science and Innovation project CHARMA: CHAracterization and ContRol of MAss Movements. A Challenge for Geohazard Mitigation (CGL2013-40828-R), and RISKNAT group (2014GR/1243).

  7. Infrasound from the 2007 fissure eruptions of Kīlauea Volcano, Hawai'i

    USGS Publications Warehouse

    Fee, D.; Garces, M.; Orr, T.; Poland, M.

    2011-01-01

    Varied acoustic signals were recorded at Kīlauea Volcano in mid-2007, coincident with dramatic changes in the volcano's activity. Prior to this time period, Pu'u 'Ō'ō crater produced near-continuous infrasonic tremor and was the primary source of degassing and lava effusion at Kīlauea. Collapse and draining of Pu'u 'Ō'ō crater in mid-June produced impulsive infrasonic signals and fluctuations in infrasonic tremor. Fissure eruptions on 19 June and 21 July were clearly located spatially and temporally using infrasound arrays. The 19 June eruption from a fissure approximately mid-way between Kīlauea's summit and Pu'u 'O'o produced infrasound for ~30 minutes-the only observed geophysical signal associated with the fissure opening. The infrasound signal from the 21 July eruption just east of Pu'u 'Ō'ō shows a clear azimuthal progression over time, indicative of fissure propagation over 12.9 hours. The total fissure propagation rate is relatively slow at 164 m/hr, although the fissure system ruptured discontinuously. Individual fissure rupture times are estimated using the acoustic data combined with visual observations.

  8. A multi-parametric approach to studying volcanic lightning utilizing LMA observations, ash characteristics, plume dynamics, seismic, and infrasound data at Sakurajima Volcano, Japan

    NASA Astrophysics Data System (ADS)

    Smith, C. M.; Van Eaton, A. R.; McNutt, S. R.; Behnke, S. A.; Cimarelli, C.; Thomas, R. J.; Edens, H. E.; Cigala, V.

    2016-12-01

    The May-June 2015 eruptive period of Sakurajima Volcano, located in southern Kyushu Province, Japan was studied using 9 Lightning Mapping Array (LMA) units, 2 broadband seismometers, 6 infrasound sensors, and video footage of the plume (infrared and lowlight). Studies were performed in cooperation with the Sakurajima Volcano Observatory. In addition, several dozen temporal ash samples were taken during multiple eruptive episodes. Volcanic lightning, especially small vent discharges, was prevalent during this eruptive period. Previous work at Sakurajima has shown relationships between overall plume charge and ash grain size as well as mineral number density and maximum seismic amplitude. We take a multi-parametric approach and examine a full suite of ash grain characteristics (including grain size distributions, particle shapes, componentry, and microlite number densities), plume heights and eruption durations, seismic and infrasound amplitudes, and the occurrence of volcanic lighting. We seek to determine the underlying relationships between commonly measured parameters and the production of volcanic lighting.

  9. Mobile Source Observation Database (MSOD)

    EPA Pesticide Factsheets

    The Mobile Source Observation Database (MSOD) is a relational database developed by the Assessment and Standards Division (ASD) of the U.S. EPA Office of Transportation and Air Quality (formerly the Office of Mobile Sources).

  10. Infrasound Sensor Calibration and Response

    DTIC Science & Technology

    2012-09-01

    functions with faster rise times. SUMMARY We have documented past work on the determination of the calibration constant of the LANL infrasound sensor...Monitoring Technologies 735 Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is estimated...National Laboratory ( LANL ) has operated an infrasound sensor calibration chamber that operates over a frequency range of 0.02 to 4 Hz. This chamber has

  11. Infrasound and seismic array analysis of snow avalanches: results from the 2015-2017 experiment in Dischma valley above Davos, Switzerland

    NASA Astrophysics Data System (ADS)

    Marchetti, Emanuele; van Herwijnen, Alec; Ripepe, Maurizio

    2017-04-01

    While flowing downhill a snow avalanche radiates seismic and infrasonic waves being coupled both with the ground and the atmosphere. Infrasound waves are mostly generated by the powder cloud of the avalanche, while seismic waves are mostly generated by the dense flowing snow mass on the ground, resulting in different energy partitioning between seismic and infrasound for different kinds of avalanches. This results into a general uncertainty on the efficiency of seismic and infrasound monitoring, in terms of the size and source-to-receiver distance of detectable events. Nevertheless, both seismic and infrasound have been used as monitoring systems for the remote detection of snow avalanches, being the reliable detection of snow avalanches of crucial importance to better understand triggering mechanisms, identify possible precursors, or improve avalanche forecasting. We present infrasonic and seismic array data collected during the winters of 2015- 2016 and 2016-2017 in the Dischma valley above Davos, Switzerland, where a five element infrasound array and a 7 element seismic array had been deployed at short distance from each other and with several avalanche paths nearby. Avalanche observation in the area is performed through automatic cameras providing additional information on the location, type (dry or wet), size and occurrence time of the avalanches released. The use of arrays instead of single sensors allows increasing the signal-to-noise ratio and identifying events in terms of back-azimuth and apparent velocity of the wave-field, thus providing indication on the source position of the recorded signal. For selected snow avalanches captured with automatic cameras, we therefore perform seismic and infrasound array processing to constrain the avalanche path and dynamics and investigate the partitioning of seismic and infrasound energy for the different portions of the avalanche path. Moreover we compare results of seismic and infrasound array processing for the

  12. On the fingerprint of ssw events in infrasound recordings at IMS stations

    NASA Astrophysics Data System (ADS)

    Ceranna, L.; Le Pichon, A.; Pilger, C.; Ross, O.

    2013-12-01

    It has been recently shown that sudden stratospheric warming (ssw) events have an impact on the detection of coherent infrasonic waves at dedicated arrays (e.g., Evers & Siegmund, 2009). During ssw events the polar vortex of prevailing stratospheric westerly winds in a winter hemisphere abruptly slows down or even reverses its direction along with an increase of stratospheric temperatures up to several tens of °C. Since infrasound arrays are mostly recording signals ducted in stratospheric wave-guides, such antennas are sensitive to changes in effective sound speed profiles - temperature plus wind speed in direction of propagation. Considering continuous infrasonic waves emitted by ocean swell (microbaroms), volcanoes or even anthropogenic sources as flares, a gap or a change in the back-azimuth of these detected signals can be observed at arrays. For the compliances with the verification of the Comprehensive Nuclear-Test-Ban Treaty a global network of 60 infrasound stations is under construction as a part of the International Monitoring System (IMS); whereas 45 have already been installed. Analysis of waveform data recorded at these stations has demonstrated the capability of infrasound as a supplementary tool for remote sensing of the atmosphere. In our study we compare the re-analysis, using PMCC, of more than five years of continuous data at all available sites (see Matoza et al., 2013) with atmospheric descriptions provided by the EMCWF. We present a synoptic view of the fingerprint of ssw events in detection of coherent signals at IMS infrasound stations both on northern and southern hemisphere, covering the full latitude range from Antarctica to Greenland.

  13. On the fingerprint of ssw events in infrasound recordings at IMS stations

    NASA Astrophysics Data System (ADS)

    Ceranna, Lars; Pilger, Christoph; Ross, Ole; Le Pichon, Alexis

    2013-04-01

    It has been recently shown that sudden stratospheric warming (ssw) events have an impact on the detection of coherent infrasonic waves at dedicated arrays (e.g., Evers & Siegmund, 2009). During ssw events the polar vortex of prevailing stratospheric westerly winds in a winter hemisphere abruptly slows down or even reverses its direction along with an increase of stratospheric temperatures up to several tens of °C. Since infrasound arrays are mostly recording signals ducted in stratospheric wave-guides, such antennas are sensitive to changes in effective sound speed profiles - temperature plus wind speed in direction of propagation. Considering continuous infrasonic waves emitted by ocean swell (microbaroms), volcanoes or even anthropogenic sources as flares, a gap or a change in the back-azimuth of these detected signals can be observed at arrays. For the compliances with the verification of the Comprehensive Nuclear-Test-Ban Treaty a global network of 60 infrasound stations is under construction as a part of the International Monitoring System (IMS); whereas 45 have already been installed. Analysis of waveform data recorded at these stations has demonstrated the capability of infrasound as a supplementary tool for remote sensing of the atmosphere. In our study we compare the re-analysis, using PMCC, of more than five years of continuous data at all available sites (see Matoza et al., 2013) with atmospheric descriptions provided by the EMCWF. We present a synoptic view of the fingerprint of ssw events in detection of coherent signals at IMS infrasound stations both on northern and southern hemisphere, covering the full latitude range from Antarctica to Greenland.

  14. Characteristics and Applications of a High Performance, Miniaturized, Infrasound Sensor

    NASA Astrophysics Data System (ADS)

    Rothman, J. L.; Marriott, D. A.

    2015-12-01

    Infrasound Sensors have been used for many years to monitor a large number of geophysical phenomena and manmade sources. Due to their large size and power consumption these sensors have typically been deployed in fixed arrays, portable arrays have required trucks to transport the sensors and support equipment. A high performance, miniaturized, infrasound microphone has been developed to enable mobile infrasound measurements that would otherwise be impractical. The new device is slightly larger than a hockey puck, weighs 200g, and consumes less than 150mW. The sensitivity is 0.4V/Pa and self noise at 1Hz is less than 0.63μPa²/Hz. The characteristics were verified using a calibrator tracable to the Los Alamos calibration chamber. Field tests have demonstrated the performance is comparable to a Chaparral model 25. Applications include man portable arrays, mobile installations, and UAV based measurements.

  15. Detection of atmospheric infrasound with a ring laser interferometer

    NASA Astrophysics Data System (ADS)

    Dunn, Robert W.; Meredith, John A.; Lamb, Angela B.; Kessler, Elijah G.

    2016-09-01

    In this paper, the results from using a large active ring laser interferometer as an infrasound detector are presented. On April 27, 2014, an EF4 tornado struck Central Arkansas and passed within 21 km of the ring laser interferometer. The tornado resulted in 16 fatalities and millions of dollars in damage. Using the ring laser to study the tornado infrasound produced results that qualitatively agree with several findings from a long-term study of weather generated infrasound by the National Oceanic and Atmospheric Administration. A Fast Fourier Transform of the ring laser output revealed a coherent frequency of approximately 0.94 Hz that lasted during the life of the storm. The 0.94 Hz frequency was initially observed 30 min before the funnel was reported on the ground. Infrasound signatures from four separate tornadoes are presented. In each case, coherent infrasound was detected at least 30 min before the tornado was reported on the ground. Examples of the detection of distant coherent acoustic-gravity waves from volcanoes and typhoons are also presented. In addition, buoyancy waves were recorded.

  16. Infrasound from Rock Fall at Santiaguito Volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Ronan, T.; Terbush, B.; Miller, A. J. C.; Anderson, J.; Johnson, J. B.

    2014-12-01

    Volcanoes generate infrasound from incidental rock fall and from rock fall directly associated with eruptions. This study demonstrates that arrays of infrasound microphones are capable of surveillance and quantification of rock fall events, including their size, location, velocity and frequency of occurrence. The study performed at Volcan Santiaguito (Guatemala) in January 2014 made use of a three element infrasound array with 30 m aperture deployed ~500 m from the active vent and ~300 m from the slide path where numerous rock falls descend. Rock fall events were detected on average 5 to 10 times per hour and were easily distinguishable from vent activity (e.g., explosions) by their dynamic back azimuth projection. As blocks tumbled down the southwest flanks of Santiaguito, sources were tracked across an azimuthal range of nearly 30 degrees, consistent with the dome's slope. Back azimuths, determined with a [progressive] multichannel cross correlation technique, are projected to the volcano's steep flanks and are used to precisely locate the source of infrasound (i.e., rocks impacting on the volcano slopes) and their velocity (10-30 m/s). Typical signals last about one minute and are characterized by cigar-shaped tremor envelopes with a predominance of energy above ~5 Hz this spectral content contrasts with Santiaguito eruption infrasound, which is peaked at ~1 Hz. Synchronous video records of the responsible rock fall confirm position and velocity and illustrate that even the smallest rock falls (estimated block size of ~1 m) are capable of producing a traceable signal. This study is a testament to the capabilities of infrasound array remote sensing for detecting volcanic unrest in the form of rock fall, which is common at most active silicic domes.

  17. Design and Operation of Infrasound Stations for Hazardous Weather Detection

    NASA Astrophysics Data System (ADS)

    Pepyne, D.

    2012-04-01

    Each year tornadoes cause property damage and death, some of which could be avoided with increased warning lead time. The year 2011 was particularly severe, with more than 1600 tornadoes causing in excess of 500 deaths in the U.S. It is known that tornadoes and their precursors generate infrasound in the 0.5Hz to 10Hz frequency band, with precursors occurring some 30-60 minutes prior to tornado touch down, which is some 15-45 minutes earlier than the average tornado warning lead time in the U.S. Given the potential of infrasound to improve tornado early warning and emergency response, the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), in conjunction with its research on small, boundary-layer observing X-band weather radars, has begun a research project whose goal is to combine the passive detection of tornado infrasound with active tracking of the parent storms that carry the tornadoes with its weather radars. In the spring of 2011 CASA conducted an infrasound field-test in Oklahoma, in the heart of the so-called "tornado-alley" where statistically the majority of springtime tornadoes in the U.S. occur. This being CASA's first infrasound experiment, the goal of the field-test was to gain an understanding of the issues involved in the design and operation of infrasound stations for severe weather monitoring and early warning. In this application, it is not so much the ability of infrasound to travel long distances that is of importance, but rather the fact that there can be precursor signals that unlike radar do not require line-of-sight to detect. In fact, for early warning, detection distance would generally need to be less than 100 km, since a propagation delay of much more than 5 minutes would be too late. Challenges encountered included persistent infrasound "clutter" from a nearby large windfarm, accurate bearing detection over a wide bandwidth with a fixed four sensor aperture, and the need to operate in the the high winds that surround

  18. Infrasound from ground to space

    NASA Astrophysics Data System (ADS)

    Bowman, Daniel Charles

    Acoustic detector networks are usually located on the Earth's surface. However, these networks suffer from shortcomings such as poor detection range and pervasive wind noise. An alternative is to deploy acoustic sensors on high altitude balloons. In theory, such platforms can resolve signals arriving from great distances, acquire others that never reach the surface at all, and avoid wind noise entirely. This dissertation focuses on scientific advances, instrumentation, and analytical techniques resulting from the development of such sensor arrays. Results from infrasound microphones deployed on balloon flights in the middle stratosphere are described, and acoustic sources such as the ocean microbarom and building ventilation systems are discussed. Electromagnetic noise originating from the balloon, flight system, and other payloads is shown to be a pervasive issue. An experiment investigating acoustic sensor calibration at low pressures is presented, and implications for high altitude recording are considered. Outstanding challenges and opportunities in sound measurement using sensors embedded in the free atmosphere are outlined. Acoustic signals from field scale explosions designed to emulate volcanic eruptions are described, and their generation mechanisms modeled. Wave forms recorded on sensors suspended from tethered helium balloons are compared with those detected on ground stations during the experiment. Finally, the Hilbert-Huang transform, a high time resolution spectral analysis method for nonstationary and nonlinear time series, is presented.

  19. A re-analysis of Carancas meteorite seismic and infrasound data based on sonic boom hypothesis

    NASA Astrophysics Data System (ADS)

    Gainville, O.; Henneton, M.; Coulouvrat, F.

    2017-06-01

    Meteoroids entering the Earth atmosphere at high hypersonic velocities are a source of sonic boom that is recorded as infrasound signal at the ground level. The Carancas meteorite (Peru, 2007) is re-examined in this way as a reference case with ground crater and nearby seismic and infrasonic recordings. A new trajectory is proposed for this meteorite by minimizing the difference between computed and observed times of arrivals for geometrical arrivals. A scenario based on diffraction is proposed to explain non-geometrical arrivals. Model frequency spectra show a reasonable agreement with data, which allows estimation of the meteorite diameter in a narrow range compatible with crater observations.

  20. Detecting blast-induced infrasound in wind noise.

    PubMed

    Howard, Wheeler B; Dillion, Kevin L; Shields, F Douglas

    2010-03-01

    Current efforts seek to monitor and investigate such naturally occurring events as volcanic eruptions, hurricanes, bolides entering the atmosphere, earthquakes, and tsunamis by the infrasound they generate. Often, detection of the infrasound signal is limited by the masking effect of wind noise. This paper describes the use of a distributed array to detect infrasound signals from four atmospheric detonations at White Sands Missile Range in New Mexico, USA in 2006. Three of the blasts occurred during times of low wind noise and were easily observed with array processing techniques. One blast was obscured by high wind conditions. The results of signal processing are presented that allowed localization of the blast-induced signals in the presence of wind noise in the array response.

  1. Hyperion 5113/A Infrasound Sensor Evaluation

    SciTech Connect

    Merchant, Bion John

    2015-09-01

    Sandia National Laboratories has tested and evaluated an infrasound sensor, the 5113/A manufactured by Hyperion. These infrasound sensors measure pressure output by a methodology developed by the University of Mississippi. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, transfer function, power, self-noise, and dynamic range. The 5113/A infrasound sensor is a new revision of the 5000 series intended to meet the infrasound application requirements for use in the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).

  2. Multidirectional seismo-acoustic wavefield of strombolian explosions at Yasur, Vanuatu using a broadband seismo-acoustic network, infrasound arrays, and infrasonic sensors on tethered balloons

    NASA Astrophysics Data System (ADS)

    Matoza, R. S.; Jolly, A. D.; Fee, D.; Johnson, R.; Kilgour, G.; Christenson, B. W.; Garaebiti, E.; Iezzi, A. M.; Austin, A.; Kennedy, B.; Fitzgerald, R.; Key, N.

    2016-12-01

    Seismo-acoustic wavefields at volcanoes contain rich information on shallow magma transport and subaerial eruption processes. Acoustic wavefields from eruptions are predicted to be directional, but sampling this wavefield directivity is challenging because infrasound sensors are usually deployed on the ground surface. We attempt to overcome this observational limitation using a novel deployment of infrasound sensors on tethered balloons in tandem with a suite of dense ground-based seismo-acoustic, geochemical, and eruption imaging instrumentation. We present preliminary results from a field experiment at Yasur Volcano, Vanuatu from July 26th to August 4th 2016. Our observations include data from a temporary network of 11 broadband seismometers, 6 single infrasonic microphones, 7 small-aperture 3-element infrasound arrays, 2 infrasound sensor packages on tethered balloons, an FTIR, a FLIR, 2 scanning Flyspecs, and various visual imaging data. An introduction to the dataset and preliminary analysis of the 3D seismo-acoustic wavefield and source process will be presented. This unprecedented dataset should provide a unique window into processes operating in the shallow magma plumbing system and their relation to subaerial eruption dynamics.

  3. Global Infrasound Association Based on Probabilistic Clutter Categorization

    NASA Astrophysics Data System (ADS)

    Arora, N. S.; Mialle, P.

    2015-12-01

    The IDC collects waveforms from a global network of infrasound sensors maintained by the IMS, and automatically detects signal onsets and associates them to form event hypotheses. However, a large number of signal onsets are due to local clutter sources such as microbaroms (from standing waves in the oceans), waterfalls, dams, gas flares, surf (ocean breaking waves) etc. These sources are either too diffuse or too local to form events. Worse still, the repetitive nature of this clutter leads to a large number of false event hypotheses due to the random matching of clutter at multiple stations. Previous studies, for example [1], have worked on categorization of clutter using long term trends on detection azimuth, frequency, and amplitude at each station. In this work we continue the same line of reasoning to build a probabilistic model of clutter that is used as part of NET-VISA [2], a Bayesian approach to network processing. The resulting model is a fusion of seismic, hydro-acoustic and infrasound processing built on a unified probabilistic framework. Notes: The attached figure shows all the unassociated arrivals detected at IMS station I09BR for 2012 distributed by azimuth and center frequency. (The title displays the bandwidth of the kernel density estimate along the azimuth and frequency dimensions).This plot shows multiple micro-barom sources as well as other sources of infrasound clutter. A diverse clutter-field such as this one is quite common for most IMS infrasound stations, and it highlights the dangers of forming events without due consideration of this source of noise. References: [1] Infrasound categorization Towards a statistics-based approach. J. Vergoz, P. Gaillard, A. Le Pichon, N. Brachet, and L. Ceranna. ITW 2011 [2] NET-VISA: Network Processing Vertically Integrated Seismic Analysis. N. S. Arora, S. Russell, and E. Sudderth. BSSA 2013.

  4. Prospects for infrasound bolide detections from balloon-borne platforms

    NASA Astrophysics Data System (ADS)

    Young, Eliot; Bowman, Daniel; Arrowsmith, Stephen; Boslough, Marc; Klein, Viliam; Ballard, Courtney; Lees, Jonathan

    2017-04-01

    We report on an experiment to assess whether balloon-borne instruments can improve sensitivities to bolides exploding in the Earth's atmosphere (essentially using the atmosphere as a witness plate to characterize the small end of the NEO (Near Earth Object) population). The CTBTO's infrasound network regularly detects infrasound disturbances caused by bolides, including the 15-FEB-2013 Chelybinsk impact. Balloon-borne infrasound sensors should have two important advantages over ground-based infrasound stations: there should be virtually no wind noise on a free-floating platform, and a sensor in the stratosphere should benefit from its location within the stratospheric duct. Balloon-borne sensors also have the disadvantage that the amplitude of infrasound waves will decrease as they ascend with altitude. To test the performance of balloon-borne sensors, we conducted an experiment on a NASA high altitude (35 km) balloon launched from Ft Sumner, NM on 28-SEP-2016. We were able to put two independent infrasound payloads on this flight. We arranged for three 3000-lb ANFO explosions to be detonated from Socorro, NM at 12:00, 14:00 and 16:29:59 MST. The first two explosions were detected from the NASA balloon, with the first explosion showing three separate waveforms arriving within a 25-s span. The peak-to-peak amplitude of the waveforms was about 0.06 Pa, and the cleanest microphone channel detected this waveform with an SNR greater than 20. A second balloon at 15 km altitude also detected the second explosion. We have signals from a dozen ground stations at various positions from Socorro to Ft Sumner. We will report on wave propagation models and how they compare with observations from the two balloons and the various ground-stations.

  5. Is there evidence for an acoustic signal at IMS infrasound stations from the North Korean event of 12 May 2010?

    NASA Astrophysics Data System (ADS)

    Koch, K.; Pilger, C.

    2016-12-01

    Over the last two years more and more evidence has been presented that a small seismic event had occurred in North Korea on 12 May 2010. Most recent work has concluded that the event shows earthquake-like features when applying event identification methods based on regional phase amplitude ratios. These findings are in contrast to previous hypotheses and identification studies which claimed that low-yield nuclear testing had been carried out. Some of these studies were based solely on radionuclide and noble gas detections found at International Monitoring System (IMS) stations as well as at national facilities. Turning to another technology, it has been shown in several studies that underground nuclear tests carried out at the Punggye-ri test site in North Korea have produced infrasound signatures at the closest IMS stations I45RU and I30JP and at national infrasound stations in South Korea. In particular this holds for the tests carried out in 2009, 2013 and 2016. For the 2013 test infrasound arrivals have been included in the Reviewed Event Bulletin (REB) issued by the International Data Center of CTBTO. Based on this experience an effort was undertaken to analyze infrasound data from these IMS stations and to search for signals that may be associated to the 12 May 2010 event. While it is not expected to obtain such a signal for an earthquake source at depth, as would not be expected as well for a buried explosion source of rather small magnitude, the analysis of I45RU and I30JP data suggests a very weak arrival as obtained from frequency-wavenumber analysis showing parameters similar to those obtained for the announced tests. If the features found are indeed not artifacts then one could speculate that (1) the event of concern may not be an earthquake, even though it exhibits seismic signal characteristics causing it to be classified as an earthquake, or (2) the detections may be related to incidental blasting activity in nearby quarries. Propagation modeling of

  6. Neural network approach to classification of infrasound signals

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Chang

    As part of the International Monitoring Systems of the Preparatory Commissions for the Comprehensive Nuclear Test-Ban Treaty Organization, the Infrasound Group at the University of Alaska Fairbanks maintains and operates two infrasound stations to monitor global nuclear activity. In addition, the group specializes in detecting and classifying the man-made and naturally produced signals recorded at both stations by computing various characterization parameters (e.g. mean of the cross correlation maxima, trace velocity, direction of arrival, and planarity values) using the in-house developed weighted least-squares algorithm. Classifying commonly observed low-frequency (0.015--0.1 Hz) signals at out stations, namely mountain associated waves and high trace-velocity signals, using traditional approach (e.g. analysis of power spectral density) presents a problem. Such signals can be separated statistically by setting a window to the trace-velocity estimate for each signal types, and the feasibility of such technique is demonstrated by displaying and comparing various summary plots (e.g. universal, seasonal and azimuthal variations) produced by analyzing infrasound data (2004--2007) from the Fairbanks and Antarctic arrays. Such plots with the availability of magnetic activity information (from the College International Geophysical Observatory located at Fairbanks, Alaska) leads to possible physical sources of the two signal types. Throughout this thesis a newly developed robust algorithm (sum of squares of variance ratios) with improved detection quality (under low signal to noise ratios) over two well-known detection algorithms (mean of the cross correlation maxima and Fisher Statistics) are investigated for its efficacy as a new detector. A neural network is examined for its ability to automatically classify the two signals described above against clutter (spurious signals with common characteristics). Four identical perceptron networks are trained and validated (with

  7. Global Infrasound Association Based on Probabilistic Clutter Categorization

    NASA Astrophysics Data System (ADS)

    Arora, Nimar; Mialle, Pierrick

    2016-04-01

    The IDC advances its methods and continuously improves its automatic system for the infrasound technology. The IDC focuses on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold by identifying ways to refine signal characterization methodology and association criteria. An objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the automatic bulletins when generating the reviewed event bulletins. Indeed, a considerable number of signal detections are due to local clutter sources such as microbaroms, waterfalls, dams, gas flares, surf (ocean breaking waves) etc. These sources are either too diffuse or too local to form events. Worse still, the repetitive nature of this clutter leads to a large number of false event hypotheses due to the random matching of clutter at multiple stations. Previous studies, for example [1], have worked on categorization of clutter using long term trends on detection azimuth, frequency, and amplitude at each station. In this work we continue the same line of reasoning to build a probabilistic model of clutter that is used as part of NETVISA [2], a Bayesian approach to network processing. The resulting model is a fusion of seismic, hydroacoustic and infrasound processing built on a unified probabilistic framework. References: [1] Infrasound categorization Towards a statistics based approach. J. Vergoz, P. Gaillard, A. Le Pichon, N. Brachet, and L. Ceranna. ITW 2011 [2] NETVISA: Network Processing Vertically Integrated Seismic Analysis. N. S. Arora, S. Russell, and E. Sudderth. BSSA 2013

  8. Incorporating numerical modeling into estimates of the detection capability of the IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Ceranna, L.; Vergoz, J.

    2012-03-01

    To monitor compliance with the Comprehensive Nuclear-Test ban Treaty (CTBT), a dedicated International Monitoring System (IMS) is being deployed. Recent global scale observations recorded by this network confirm that its detection capability is highly variable in space and time. Previous studies estimated the radiated source energy from remote observations using empirical yield-scaling relations which account for the along-path stratospheric winds. Although the empirical wind correction reduces the variance in the explosive energy versus pressure relationship, strong variability remains in the yield estimate. Today, numerical modeling techniques provide a basis to better understand the role of different factors describing the source and the atmosphere that influence propagation predictions. In this study, the effects of the source frequency and the stratospheric wind speed are simulated. In order to characterize fine-scale atmospheric structures which are excluded from the current atmospheric specifications, model predictions are further enhanced by the addition of perturbation terms. A theoretical attenuation relation is thus developed from massive numerical simulations using the Parabolic Equation method. Compared with previous studies, our approach provides a more realistic physical description of long-range infrasound propagation. We obtain a new relation combining a near-field and a far-field term, which account for the effects of both geometrical spreading and absorption. In the context of the future verification of the CTBT, the derived attenuation relation quantifies the spatial and temporal variability of the IMS infrasound network performance in higher resolution, and will be helpful for the design and prioritizing maintenance of any arbitrary infrasound monitoring network.

  9. Mobile Source Observation Database (MSOD)

    EPA Pesticide Factsheets

    The Mobile Source Observation Database (MSOD) is a relational database being developed by the Assessment and Standards Division (ASD) of the US Environmental Protection Agency Office of Transportation and Air Quality (formerly the Office of Mobile Sources). The MSOD contains emission test data from in-use mobile air- pollution sources such as cars, trucks, and engines from trucks and nonroad vehicles. Data in the database was collected from 1982 to the present. The data is intended to be representative of in-use vehicle emissions in the United States.

  10. Infrasound analysis of I18DK, northwest Greenland

    NASA Astrophysics Data System (ADS)

    Evers, L. G.; Weemstra, C.

    2010-12-01

    Within the scope of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), four methods are used to verify the treaty. One of these methods is based on the detection of infrasound waves generated by a nuclear explosion. Seismological, hydroacoustical and radionuclide measurements are also applied. The International Monitoring System (IMS) will consist of 60 infrasound stations of which 35 stations are currently operational. Data obtained from an infrasound station situated on the northwestern shoreline of Greenland is analyzed. This station is operated by Denmark and labeled as I18DK. I18DK is situated in an area which receives an ever increasing attention from a geophysical perspective. I18DK has continuously been operational from April 2003 and onwards. The IMS station is an infrasound array with an aperture of about 1200 meters, where air-pressure fluctuations are recorded by eight microbarometers at a sample-rate of 20 Hz. The infrasonic recordings are filtered between 0.1 & 1.0 and 1.0 & 6.0 Hz. The slowness grid is searched for two different configurations in the higher frequency band. Once using all 8 stations and once only taking into account the 5 center stations. Several different source types are known to generate infrasound, for example, calving of icebergs and glaciers, explosions, earthquakes, oceanic wave-wave interaction, volcanic eruptions and aurora. The challenge is to distinguish between these different source types and use the outcome of the array analysis to better understand these phenomena. The rate of occurrence of icequakes, the calving of glaciers and the variation in extent of the sea ice in this area is of interest in relation to global warming. The processing results of the 1 to 6 Hz band seem to show dominating back-azimuths related to these sources. The glaciers south of I18DK produce significant infrasound during summer time. As well, a direct link can be found between the number of warm days in a year and the number of infrasound

  11. Joint interpretation of infrasound, acoustic, and seismic waves from meteorites: Chelyabinsk bolide and other events

    NASA Astrophysics Data System (ADS)

    Kitov, Ivan; Rozhkov, Mikhail; Bobrov, Dmitry; Ovtchinnikov, Vladimir

    2014-05-01

    Meteorites are always the events that testing the capability of the International Monitoring System to measure and the International Data Centre to analyze sources similar to nuclear explosions. Monitoring of the Comprehensive Nuclear-Test-Ban Treaty suggests the possibility to detect infrasound (acoustic) and seismic signals from atmospheric and underground events and to locate their sources. Chelyabinsk meteor was one of the best exemplar in a row of other atmospheric events exposing the ability of IDC and IMS to handle the atmospheric explosions. The uniqueness of this event is that the generated seismic, acousto-seismic and infrasound wave fields were recorded by considerable number of IMS stations of different technologies at wide distance range. The shock waves from the Chelyabinsk meteor generated an I-phase recorded by IMS infrasound stations and a series of seismic phases. The Pn-waves were observed by five near-regional seismic stations together with Sn- and Lg-waves. They are most likely associated with the impact of the meteor debris and the location associated with their source differs by tens of kilometers from that obtained by Rayleigh and Love waves. The latter were generated by acoustic (low-amplitude shock) waves hitting the ground beneath the trajectory of the meteor. Surprisingly, these surface waves associated with the meteor and observed at least at distances of 45º were not associated with the event in the Reviewed Event Bulletin. This implies a conceptual gap in the IDC processing and fusion of acoustic and seismic waves. The trajectory of the meteorite built with the epicenters of seismic, acousto-seismic and infrasound events is in good compliance with the trajectories built by different scientific institutions including NASA. We present an approximate distribution of energy release along the trajectory and thus the amplitude of the generated shock wave. It allows interpreting the period and amplitude dependence of the LR and LQ waves on

  12. Balloon Borne Infrasound Platforms for Remote Monitoring of Natural Hazards

    NASA Astrophysics Data System (ADS)

    Lees, J. M.; Bowman, D. C.

    2016-12-01

    In the last three years several NASA supported balloon launches were instrumented with infrasound sensors to monitor acoustic wavefields in the stratosphere. Such high altitude platforms may detect geoacoustic phenomena at much greater ranges than equivalent ground stations, and perhaps record sound waves that rarely reach the Earth's surface. Since acoustic waves are a key diagnostic for several natural hazards (volcanic eruptions, severe storms, and tsunamis, for example), the increased range and spatial coverage of balloon borne arrays promise greater quantification and perhaps early warning of such events. Before this can be accomplished, the performance of stratospheric arrays must be compared to tthat of those on the ground. Here, we show evidence for 0.2 Hz infrasound associated with oceanic oscillations recorded during night time hours of the flights, consistent with concurrent ground recordings on the east and west coasts of North America. We also report numerous narrow band acoustic signals (5-30 Hz) that resemble recordings made in in the 1960's, the last time microphones were lofted into the stratosphere. Theoretical and ground based observational data from Rind(1977) indicate loss of acoustic energy in the thermosphere, where heating of the upper atmosphere is predicted to be on the order of 30-40 degrees Kelvin per day. We propose testing these ideas by using extensive ground arrays recently deployed in North America in conjunction with airborne platforms installed in the mid-stratosphere. New experiments scheduled for 2016 include circumnavigation of Antarctica (collected in June) as well as two proposed flights in New Mexico in September. The flights are designed to both capture known acoustic sources as well as events of opportunity.

  13. Using Hilbert-Huang Transform (HHT) to Extract Infrasound Generated by the 2013 Lushan Earthquake in China

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Xu, Q.; Liu, H. X.

    2017-03-01

    We applied the Hilbert-Huang transform (HHT) method to extract the infrasound generated by the 2013 Lushan earthquake and its following aftershocks in China from a nearly continuous infrasound recode made 130 km from the earthquake epicenter. An improved STA/LTA algorithm was adopted for detecting the ambient infrasonic events from the data record. A powerful processing technique for non-stationary signal, the HHT, was applied to extract the significant intrinsic mode functions (IMFs) of the infrasonic signal associated with the earthquakes. The features of the extracted IMFs, such as the dominant frequency, the maximum amplitude and the spectral entropy, were investigated using Hilbert spectral analysis. Regression analysis between the maximum amplitude in the infrasound spectra and the magnitudes of the earthquakes was carried out to verify the source of the infrasound events detected. The results demonstrated that the HHT method could successfully identify the infrasound related to the earthquakes.

  14. Volcanic eruption volume flux estimations from very long period infrasound signals

    NASA Astrophysics Data System (ADS)

    Yamada, Taishi; Aoyama, Hiroshi; Nishimura, Takeshi; Iguchi, Masato; Hendrasto, Muhamad

    2017-01-01

    We examine very long period infrasonic signals accompanying volcanic eruptions near active vents at Lokon-Empung volcano in Indonesia, Aso, Kuchinoerabujima, and Kirishima volcanoes in Japan. The excitation of the very long period pulse is associated with an explosion, the emerging of an eruption column, and a pyroclastic density current. We model the excitation of the infrasound pulse, assuming a monopole source, to quantify the volume flux and cumulative volume of erupting material. The infrasound-derived volume flux and cumulative volume can be less than half of the video-derived results. A largely positive correlation can be seen between the infrasound-derived volume flux and the maximum eruption column height. Therefore, our result suggests that the analysis of very long period volcanic infrasound pulses can be helpful in estimating the maximum eruption column height.

  15. Hyperion 5113/GP Infrasound Sensor Evaluation.

    SciTech Connect

    Merchant, Bion J.

    2015-08-01

    Sandia National Laboratories has tested and evaluated an infrasound sensor, the 5113/GP manufactured by Hyperion. These infrasound sensors measure pressure output by a methodology developed by the University of Mississippi. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, transfer function, power, self-noise, dynamic range, and seismic sensitivity. These sensors are being evaluated prior to deployment by the U.S. Air Force.

  16. On modeling internal gravity wave dynamics from infrasound propagation

    NASA Astrophysics Data System (ADS)

    Ribstein, Bruno; Millet, Christophe; Lott, Francois

    2017-04-01

    Low frequency acoustic waves (infrasounds) are generally used to remotely detect strong explosions, using their possibility of long-distance and coherent propagation. Numerical prediction of infrasounds is a complex issue due to constantly changing atmospheric conditions and to the random nature of small-scale flows. Although it is well-known that part of the upward propagating wave is refracted at stratospheric levels, where gravity waves significantly affect both the temperature and the wind, yet the process by which the gravity wave field changes some infrasound arrivals remains not well understood. In the present work, we use a stochastic parameterization to model the subgrid scale gravity wave field from atmospheric states provided by ECMWF. Numerical evidence are presented showing that regardless of whether the superimposed gravity wave field possesses relatively small or large features the sensitivity of ground-based infrasound signals can be significantly different. A version of the gravity wave parameterization previously tuned by co-authors for climate modeling purpose is shown to not retrieve the duration of recorded acoustic signals. A new version of the wave-parameterization is here proposed which more accurately predict the small scale content of gravity wave fields, especially in the middle atmosphere. Compare to other semi-empirical approaches one value of this new parameterization is that the gravity wave drag obtained is in agreement with observations.

  17. Ultraviolet observations of astronomical sources

    NASA Technical Reports Server (NTRS)

    Eaton, Joel A.

    1994-01-01

    The final report on 'Ultraviolet Observations of Astronomical Sources,' which ran for a total of three years, roughly between 1 July 1988 and 14 Feb. 1993 is presented. During the first year, I worked at Indiana University; since October, 1989, I have been at Tennessee State University. This grant has supported my studies of archival International Ultraviolet Explorer (IUE) observations of zeta Aur binaries, cool stars that are paired with hot stars in binary systems. Such systems are important as a source of detailed knowledge about the structures of chromospheres and winds in cool giant and supergiant stars, since the hot star serves as a probe of many lines of sight through the cool supergiant star's outer atmosphere. By determining the physical conditions along many such lines of sight, a detailed two-dimensional map of the chromosphere and wind may be constructed. The grant grew out of my analysis of archival IUE observations of 31 Cyg in which I analyzed five epochs of an atmospheric eclipse that occurred in 1982. I fit the attenuation spectra of atmospheric eclipse throughout the ultraviolet (lambda(lambda)1175-1950 and lambda(lambda)2500-3100) with theoretically calculated spectra, thereby determining the physical properties of gas (mass column density of absorbers, temperature, and velocity spread) along each observed line of sight. A similar analysis for other such zeta Aur binaries was accomplished and theoretical models for the chromospheres of these stars based on my observations were constructed.

  18. MB3a Infrasound Sensor Evaluation.

    SciTech Connect

    Merchant, Bion J.; McDowell, Kyle D.

    2014-11-01

    Sandia National Laboratories has tested and evaluated a new infrasound sensor, the MB3a, manufactured by Seismo Wave. These infrasound sensors measure pressure output by a methodology developed by researchers at the French Alternative Energies and Atomic Energy Commission (CEA) and the technology was recently licensed to Seismo Wave for production and sales. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, transfer function, power, self-noise, dynamic range, seismic sensitivity, and self- calibration ability. The MB3a infrasound sensors are being evaluated for potential use in the International Monitoring System (IMS) of the Comprehensive Nuclear Test-Ban-Treaty Organization (CTBTO).

  19. Dynamic Modeling of Infrasound Generation from Vulcanian Explosions

    NASA Astrophysics Data System (ADS)

    Watson, L. M.; Dunham, E. M.

    2015-12-01

    Volcano infrasound provides a complementary view of volcanic processes to seismic waves, as the atmosphere exhibits contrasting wave propagation characteristics to the crust. Potential benefits include a more uniform velocity structure, shorter wavelengths enabling better spatial resolution, and lower attenuation improving remote monitoring capabilities. Recent work on volcano infrasound has employed kinematic source descriptions, in terms of such quantities as mass flux for a monopole point source. Such descriptions are quite useful for the inverse problem of inferring mass flux from infrasound data. In this study, we introduce a dynamic source model incorporating the physical processes that determine how the cloud of eruptive gas and ash expands outward to generate the infrasound signal. Our dynamic source model could ultimately be coupled to an unsteady conduit flow model, providing a means to infer more details of the eruption process from recorded infrasound signals. Our model describes a vulcanian eruption where mass is ejected into the atmosphere forming a cloud of gas and ash. Infrasonic acoustic waves are generated by the expansion of the cloud. The model goes beyond linear acoustics by accounting for nonlinear terms in the compressible Euler equations for the surrounding atmosphere. The model presently consists of a system of nonlinear ordinary differential equations, expressing the balance of mass, momentum, and energy, that can be solved for the evolution of the radius of the cloud and pressure and temperature within it. Entrainment and heat exchange with the surrounding atmospheric air can be accounted for. Our analysis is inspired by similar models of underwater explosions (Gilmore, 1952) and seismic air-guns (Ziolkowski, 1970). We aim to use the model to investigate how acoustic signals change when volcano properties, such as vent geometry, are varied. Our longer-term goal is to couple the atmospheric infrasound model presented here to an unsteady

  20. Generating regional infrasound celerity-range models using ground-truth information and the implications for event location

    NASA Astrophysics Data System (ADS)

    Nippress, Alexandra; Green, David N.; Marcillo, Omar E.; Arrowsmith, Stephen J.

    2014-05-01

    Celerity-range models, where celerity is defined as the epicentral distance divided by the total traveltime (similar to the definition of group velocity for dispersed seismic surface waves), can be used for the association of infrasound automatic detections, for event location and for the validation of acoustic propagation simulations. Signals recorded from ground truth events are used to establish celerity-range models, but data coverage is uneven in both space and time. To achieve a high density of regional recordings we use data from USArray seismic stations recording air-to-ground coupled waves from explosions during the summers of 2004-2008 at the Utah Training and Test Range, in the western United States, together with data from five microbarograph arrays at regional distances (<1000 km). We have developed a consistent methodology for analysing the infrasound and seismic data, including choosing filter characteristics from a limited group of two-octave wide filter bands and picking the maximum peak-to-peak arrival. We clearly observe tropospheric, thermospheric and stratospheric arrivals, in agreement with regional ray tracing models. Due to data availability and the dependence of infrasound propagation on the season, we develop three regional celerity-range models for the U.S. summer, with a total of 2211 data picks. The new models suggest event locations using the Geiger method could be improved in terms of both accuracy (up to 80 per cent closer to ground truth) and precision (error ellipse area reduced by >90 per cent) when compared to those estimated using the global International Data Center model, particularly for events where stations detect arrivals at ranges <350 km. Whilst adding data-based prior information into the Bayesian Infrasound Source Localization (BISL) method is also shown to increase precision, to increase accuracy, the parameter space must be expanded to include station-specific celerity distributions.

  1. An analysis of three new infrasound arrays around Kīlauea Volcano

    USGS Publications Warehouse

    Thelen, Weston A.; Cooper, Jennifer

    2015-01-01

    A network of three new infrasound station arrays was installed around Kīlauea Volcano between July 2012 and September 2012, and a preliminary analysis of open-vent monitoring has been completed by Hawaiian Volcano Observatory (HVO). Infrasound is an emerging monitoring method in volcanology that detects perturbations in atmospheric pressure at frequencies below 20 Hz, which can result from volcanic events that are not always observed optically or thermally. Each array has the capability to detect various infrasound events as small as 0.05 Pa as measured at the array site. The infrasound monitoring network capabilities are demonstrated through case studies of rockfalls, pit collapses, and rise-fall cycles at Halema'uma'u Crater and Pu'u 'Ōʻō.

  2. High Altitude Infrasound Measurements using Balloon-Borne Arrays

    NASA Astrophysics Data System (ADS)

    Bowman, D. C.; Johnson, C. S.; Gupta, R. A.; Anderson, J.; Lees, J. M.; Drob, D. P.; Phillips, D.

    2015-12-01

    For the last fifty years, almost all infrasound sensors have been located on the Earth's surface. A few experiments consisting of microphones on poles and tethered aerostats comprise the remainder. Such surface and near-surface arrays likely do not capture the full diversity of acoustic signals in the atmosphere. Here, we describe results from a balloon mounted infrasound array that reached altitudes of up to 38 km (the middle stratosphere). The balloon drifted at the ambient wind speed, resulting in a near total reduction in wind noise. Signals consistent with tropospheric turbulence were detected. A spectral peak in the ocean microbarom range (0.12 - 0.35 Hz) was present on balloon-mounted sensors but not on static infrasound stations near the flight path. A strong 18 Hz signal, possibly related to building ventilation systems, was observed in the stratosphere. A wide variety of other narrow band acoustic signals of uncertain provenance were present throughout the flight, but were absent in simultaneous recordings from nearby ground stations. Similar phenomena were present in spectrograms from the last balloon infrasound campaign in the 1960s. Our results suggest that the infrasonic wave field in the stratosphere is very different from that which is readily detectable on surface stations. This has implications for modeling acoustic energy transfer between the lower and upper atmosphere as well as the detection of novel acoustic signals that never reach the ground. Our work provides valuable constraints on a proposed mission to detect earthquakes on Venus using balloon-borne infrasound sensors.

  3. Application of a New Infrasound Sensor Technology in a Long Range Infrasound Propagation Experiment

    NASA Astrophysics Data System (ADS)

    Talmadge, C. L.; Waxler, R.; Hetzer, C. H.; Kleniert, D. E., Jr.; Dillion, K.; Assink, J.; Aydin, A.

    2009-12-01

    A low-cost ruggedized infrasound sensor has been developed at the NCPA laboratory of the University of Mississippi for outdoor infrasound measurements. This sensor has similar performance characteristics to other "standard" infrasound sensors, such as the Chaparral 50. A total of 50 sensors were constructed for this experiment, of which 42 were deployed on the Nevada and Utah desert for a period of four months. A long-range infrasound propagation experiment using these sensors was performed during the summer and fall of 2009. Source sizes varied in size from 4, 20 and 80 equivalent tons of TNT. The blasts were carried out typically on the Monday of each week in the afternoon, and were part of a scheduled demolition of first, second and third stages of trident missiles. In addition to a source capture location 23-km south of the site of the blasts, a series of 8 5-element arrays are located to the west of the blast location, at approximate ranges of 180 through 250 km in 10-km steps. Each array consisted of elements at -150-m, -50-m, 0-m, 50-m and 150-m relative to the center of the array along an east-west direction, and all microphones were equipped with 4 50-ft porous hoses connected to the microphone manifold for wind noise suppression. The signals from the microphones were digitized using GPS-synchronized, 24-bit DAQ systems. A Westerly direction for the deployment of the microphones was motivated by the presence of a strong stratospheric duct that persists through the summer months in the northern hemisphere at these latitudes. In this paper, we will discuss feasibility issues related the design of the NCPA microphone that makes possible deployments on these on large scales. Signal to noise issues related to temperature and wind fluctuations will also be discussed. Future plans include a larger scale deployment of several hundred microphones during 2010. We will discuss how the lessons learned from this series of measurements impacts that future deployment.

  4. Infrasound Detection of Rocket Launches

    DTIC Science & Technology

    2000-09-01

    were examined for 14 VAFB launches in 1999 at SGAR (680 km) and DLIAR (1300 km). Detections were seen for a Titan IVB launched 5/22/99 and a Delta II...size. Upper atmospheric wind conditions should have been favorable for several of the detections, however noise levels were often high at SGAR and...phase velocities are consistent with stratospheric propagation and nominal infrasound travel times to SGAR (2340 s) and DLIAR (4440 s). The signals were

  5. Infrasound Sensor Models and Evaluations

    SciTech Connect

    KROMER,RICHARD P.; MCDONALD,TIMOTHY S.

    2000-07-31

    Sandia National Laboratories has continued to evaluate the performance of infrasound sensors that are candidates for use by the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty Organization. The performance criteria against which these sensors are assessed are specified in ``Operational Manual for Infra-sound Monitoring and the International Exchange of Infrasound Data''. This presentation includes the results of efforts concerning two of these sensors: (1) Chaparral Physics Model 5; and (2) CEA MB2000. Sandia is working with Chaparral Physics in order to improve the capability of the Model 5 (a prototype sensor) to be calibrated and evaluated. With the assistance of the Scripps Institution of Oceanography, Sandia is also conducting tests to evaluate the performance of the CEA MB2000. Sensor models based on theoretical transfer functions and manufacturer specifications for these two devices have been developed. This presentation will feature the results of coherence-based data analysis of signals from a huddle test, utilizing several sensors of both types, in order to verify the sensor performance.

  6. Could the IMS Infrasound Stations Support a Global Network of Small Aperture Seismic Arrays?

    NASA Astrophysics Data System (ADS)

    J, Gibbons, Steven; Kværna, Tormod; Mykkeltveit, Svein

    2015-04-01

    find such added capabilities valuable from a national perspective. In addition, the seismic recordings may also help to identify the sources of infrasound signals with consequences for improved event screening and evaluating models of infrasound propagation and atmospheric properties.

  7. Infrasound and the avian navigational map

    USGS Publications Warehouse

    Hagstrum, J.T.

    2001-01-01

    Birds can accurately navigate over hundreds to thousands of kilometres, and use celestial and magnetic compass senses to orient their flight. How birds determine their location in order to select the correct homeward bearing (map sense) remains controversial, and has been attributed to their olfactory or magnetic senses. Pigeons can hear infrasound down to 0??05 Hz, and an acoustic avian map is proposed consisting of infrasonic cues radiated from steep-sided topographic features. The source of these infrasonic signals is microseisms continuously generated by interfering oceanic waves. Atmospheric processes affecting the infrasonic map cues can explain perplexing experimental results from pigeon releases. Moreover, four recent disrupted pigeon races in Europe and the north-eastern USA intersected infrasonic shock waves from the Concorde supersonic transport. Having an acoustic map might also allow clock-shifted birds to test their homeward progress and select between their magnetic and solar compasses.

  8. Assessing and optimizing the performance of infrasound networks to monitor volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Le Pichon, Alexis; Marchetti, Emanuele; Assink, Jelle; Vergniolle, Sylvie

    2017-01-01

    We propose a numerical modeling technique based on a frequency-dependent attenuation relation to assess, quantify and optimize the performance of any arbitrary infrasound network to monitor explosive sources such as volcanic eruptions. Simulations are further enhanced by including realistic sources and propagation effects. We apply our approach to both hemispheres by considering the Euro-Mediterranean and the Eastern Australian regions. In these regions, we use quasi-permanent infrasound signals from Mt. Etna recorded in Tunisia and from Mt. Yasur recorded in New Caledonia. These well-instrumented volcanoes offer a unique opportunity to validate our attenuation model. In particular, accurate comparisons between near- and far-field recordings demonstrate the potential of the proposed methodology to remotely monitor volcanoes. A good agreement is found between modeled and observed results, especially when incorporating representative 10 m s-1 wind perturbations in the atmospheric specifications according to previous campaign measurements. To optimize the network layout in order to ensure the best monitoring of the volcanoes, we proceed through a grid search to find optimum locations of an additional array. We show that adding one array at an appropriate location in both regions under study could significantly improve detections half of the year. The application of the proposed methodology can provide in near real-time a realistic confidence level of volcanic eruption detections, useful to mitigate the risk of aircrafts encountering volcanic ash.

  9. Assessing and optimizing the performance of infrasound networks to monitor volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Pichon, Alexis Le; Marchetti, Emanuele; Assink, Jelle; Vergniolle, Sylvie

    2016-10-01

    We propose a numerical modeling technique based on a frequency-dependent attenuation relation to assess, quantify and optimize the performance of any arbitrary infrasound network to monitor explosive sources such as volcanic eruptions. Simulations are further enhanced by including realistic sources and propagation effects. We apply our approach to both hemispheres by considering the Euro-Mediterranean and the Eastern Australian regions. In these regions, we use quasi-permanent infrasound signals from Mt. Etna recorded in Tunisia and from Mt. Yasur recorded in New Caledonia. These well-instrumented volcanoes offer a unique opportunity to validate our attenuation model. In particular, accurate comparisons between near and far-field recordings demonstrate the potential of the proposed methodology to remotely monitor volcanoes. A good agreement is found between modeled and observed results, especially when incorporating representative 10 m/s wind perturbations in the atmospheric specifications according to previous campaign measurements. To optimize the network layout in order to ensure the best monitoring of the volcanoes, we proceed through a grid search to find optimum locations of an additional array. We show that adding one array at an appropriate location in both regions under study could significantly improve detections half of the year. The application of the proposed methodology can provide in near real-time a realistic confidence level of volcanic eruption detections, useful to mitigate the risk of aircrafts encountering volcanic ash.

  10. Detecting hidden volcanic explosions from Mt. Cleveland Volcano, Alaska with infrasound and ground-couples airwaves

    USGS Publications Warehouse

    De Angelis, Slivio; Fee, David; Haney, Matthew; Schneider, David

    2012-01-01

    In Alaska, where many active volcanoes exist without ground-based instrumentation, the use of techniques suitable for distant monitoring is pivotal. In this study we report regional-scale seismic and infrasound observations of volcanic activity at Mt. Cleveland between December 2011 and August 2012. During this period, twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent, and ground-coupled acoustic waves were recorded at seismic stations across the Aleutian Arc. Several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data. However, many explosions eluded initial, automated, analyses of satellite data due to poor weather conditions. Infrasound and seismic monitoring provided effective means for detecting these hidden events. We present results from the implementation of automatic infrasound and seismo-acoustic eruption detection algorithms, and review the challenges of real-time volcano monitoring operations in remote regions. We also model acoustic propagation in the Northern Pacific, showing how tropospheric ducting effects allow infrasound to travel long distances across the Aleutian Arc. The successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the Aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at Mt. Cleveland.

  11. Analysis of infrasound waves generated by the May 2012 earthquake sequence in Northen Italy

    NASA Astrophysics Data System (ADS)

    Marchetti, E.; Ripepe, M.; Le Pichon, A.; Lacanna, G.; Piccinini, D.

    2013-12-01

    In May 2012 a 5.9 ML earthquake occurred in Northern Italy with the sequence of major quakes (Ml>5.4) clearly felt in Northern and Central Italy. Almost 2000 earthquakes, with local magnitude ranging between 1 and 5.9, were recorded in one month, and were typically associated with shallow (<10 km) inverse faults. We present analysis of pressure waves generated by these earthquakes and recorded at epicentral distances of ~200 km southward, at the large (1.4 km) aperture AMT array in Central Italy, and of ~300 km westward, at the small (130 m) aperture CHA array, operating in the northwestern Italian Alps mostly for snow avalanche monitoring. Infrasound is recorded for events with varying magnitude (Ml >4) and depth (5-15 km), and appears to be composed both of epicentral infrasound, produced at the source, and secondary infrasound, produced by the shaking of topography around the source. The robust infrasound dataset and the optimal recording condition, with downwind propagation to the CHA array, allow to carefully investigate the origin of the infrasonic radiation. Back-propagation of infrasonic detections points to a maximum infrasound radiation along an extended area in the PO valley. The relationship between infrasonic emission and earthquake source parameters such as magnitude, depth, focal mechanism and directivity, are analyzed for small-to-moderate magnitude earthquakes. Given the large distance among IMS infrasonic arrays, the relationship between infrasound and earthquakes is not well documented yet and mainly restricted to ML>7 earthquake, and thus still debated. Accordingly, the present study, that integrates within the FP7 ARISE design study project (Atmospheric dynamics Research InfraStructure in Europe), represents a good opportunity to investigate such a topic given the robust seismological constraints and optimal infrasound records.

  12. The early March 2016 Sudden Stratospheric Warming observed in data recorded by a ground-based high-latitude instrument cluster

    NASA Astrophysics Data System (ADS)

    Näsholm, Sven Peter; Hildebrand, Jens; E Hibbins, Robert; Kero, Johan; Stober, Gunter; Smets, Pieter M.; Le Pichon, Alexis; Gibbons, Steven J.; Espy, Patrick J.; Belova, Evgenia; Kværna, Tormod; Baumgarten, Gerd

    2017-04-01

    This data-based presentation shows tropospheric, stratospheric, mesospheric, and lower thermospheric observations related to the atmospheric dynamics and temperature before, during, and after the early March 2016 Sudden Stratospheric Warming (SSW). These observations are done by analyzing recordings at a Scandinavian cluster of high-latitude ground-based stations which comprises Doppler lidar (Andenes, Norway), meteor radar (Andenes, Norway; Kiruna, Sweden; Trondheim, Norway), infrasound (Bardufoss, Norway), and MST radar (Andenes, Norway; Kiruna, Sweden) instrumentation. In addition, we display the related stratospheric winds and temperatures given by re-analysis products. These indicate the availability of stratospheric infrasound ducts as function of time and backazimuth direction between oceanic microbarom sources and the infrasound station - hence supporting the observation of the SSW in the infrasound data. The stratospheric-related and the mesospheric-related observations all show clear indications of a rapid change in atmospheric dynamics around March 6, 2016.

  13. CTBT infrasound network performance to detect the 2013 Russian fireball event

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars; Ross, J. Ole; Le Pichon, Alexis; Mialle, Pierrick; Garcés, Milton A.

    2015-04-01

    The explosive fragmentation of the 2013 Chelyabinsk meteorite generated a large airburst with an equivalent yield of 500 kT TNT. It is the most energetic event recorded by the infrasound component of the Comprehensive Nuclear-Test-Ban Treaty-International Monitoring System (CTBT-IMS), globally detected by 20 out of 42 operational stations. This study performs a station-by-station estimation of the IMS detection capability to explain infrasound detections and nondetections from short to long distances, using the Chelyabinsk meteorite as global reference event. Investigated parameters influencing the detection capability are the directivity of the line source signal, the ducting of acoustic energy, and the individual noise conditions at each station. Findings include a clear detection preference for stations perpendicular to the meteorite trajectory, even over large distances. Only a weak influence of stratospheric ducting is observed for this low-frequency case. Furthermore, a strong dependence on the diurnal variability of background noise levels at each station is observed, favoring nocturnal detections.

  14. CTBT infrasound network performance to detect the 2013 Russian fireball event

    DOE PAGES

    Pilger, Christoph; Ceranna, Lars; Ross, J. Ole; ...

    2015-03-18

    The explosive fragmentation of the 2013 Chelyabinsk meteorite generated a large airburst with an equivalent yield of 500 kT TNT. It is the most energetic event recorded by the infrasound component of the Comprehensive Nuclear-Test-Ban Treaty-International Monitoring System (CTBT-IMS), globally detected by 20 out of 42 operational stations. This study performs a station-by-station estimation of the IMS detection capability to explain infrasound detections and nondetections from short to long distances, using the Chelyabinsk meteorite as global reference event. Investigated parameters influencing the detection capability are the directivity of the line source signal, the ducting of acoustic energy, and the individualmore » noise conditions at each station. Findings include a clear detection preference for stations perpendicular to the meteorite trajectory, even over large distances. Only a weak influence of stratospheric ducting is observed for this low-frequency case. As a result, a strong dependence on the diurnal variability of background noise levels at each station is observed, favoring nocturnal detections.« less

  15. CTBT infrasound network performance to detect the 2013 Russian fireball event

    SciTech Connect

    Pilger, Christoph; Ceranna, Lars; Ross, J. Ole; Le Pichon, Alexis; Mialle, Pierrick

    2015-03-18

    The explosive fragmentation of the 2013 Chelyabinsk meteorite generated a large airburst with an equivalent yield of 500 kT TNT. It is the most energetic event recorded by the infrasound component of the Comprehensive Nuclear-Test-Ban Treaty-International Monitoring System (CTBT-IMS), globally detected by 20 out of 42 operational stations. This study performs a station-by-station estimation of the IMS detection capability to explain infrasound detections and nondetections from short to long distances, using the Chelyabinsk meteorite as global reference event. Investigated parameters influencing the detection capability are the directivity of the line source signal, the ducting of acoustic energy, and the individual noise conditions at each station. Findings include a clear detection preference for stations perpendicular to the meteorite trajectory, even over large distances. Only a weak influence of stratospheric ducting is observed for this low-frequency case. As a result, a strong dependence on the diurnal variability of background noise levels at each station is observed, favoring nocturnal detections.

  16. The stratospheric arrival pair in infrasound propagation.

    PubMed

    Waxler, Roger; Evers, Läslo G; Assink, Jelle; Blom, Phillip

    2015-04-01

    The ideal case of a deep and well-formed stratospheric duct for long range infrasound propagation in the absence of tropospheric ducting is considered. A canonical form, that of a pair of arrivals, for ground returns of impulsive signals in a stratospheric duct is determined. The canonical form is derived from the geometrical acoustics approximation, and is validated and extended through full wave modeling. The full caustic structure of the field of ray paths is found and used to determine phase relations between the contributions to the wavetrain from different propagation paths. Finally, comparison with data collected from the 2005 fuel gas depot explosion in Buncefield, England is made. The correspondence between the theoretical results and the observations is shown to be quite good.

  17. Assessing the detection capability of a dense infrasound network in the southern Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Che, Il-Young; Le Pichon, Alexis; Kim, Kwangsu; Shin, In-Cheol

    2017-08-01

    The Korea Infrasound Network (KIN) is a dense seismoacoustic array network consisting of eight small-aperture arrays with an average interarray spacing of ∼100 km. The processing of the KIN historical recordings over 10 yr in the 0.05-5 Hz frequency band shows that the dominant sources of signals are microbaroms and human activities. The number of detections correlates well with the seasonal and daily variability of the stratospheric wind dynamics. The quantification of the spatiotemporal variability of the KIN detection performance is simulated using a frequency-dependent semi-empirical propagation modelling technique. The average detection thresholds predicted for the region of interest by using both the KIN arrays and the International Monitoring System (IMS) infrasound station network at a given frequency of 1.6 Hz are estimated to be 5.6 and 10.0 Pa for two- and three-station coverage, respectively, which was about three times lower than the thresholds predicted by using only the IMS stations. The network performance is significantly enhanced from May to August, with detection thresholds being one order of magnitude lower than the rest of the year due to prevailing steady stratospheric winds. To validate the simulations, the amplitudes of ground-truth repeated surface mining explosions at an open-pit limestone mine were measured over a 19-month period. Focusing on the spatiotemporal variability of the stratospheric winds which control to first order where infrasound signals are expected to be detected, the predicted detectable signal amplitude at the mine and the detection capability at one KIN array located at a distance of 175 km are found to be in good agreement with the observations from the measurement campaign. The detection threshold in summer is ∼2 Pa and increases up to ∼300 Pa in winter. Compared with the low and stable thresholds in summer, the high temporal variability of the KIN performance is well predicted throughout the year. Simulations

  18. Characterization of Atmospheric Infrasound for Improved Weather Monitoring

    NASA Astrophysics Data System (ADS)

    Threatt, Arnesha; Elbing, Brian

    2016-11-01

    Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD MAP) is a multi-university collaboration focused on development and implementation of unmanned aircraft systems (UAS) and integration with sensors for atmospheric measurements. A primary objective for this project is to create and demonstrate UAS capabilities needed to support UAS operating in extreme conditions, such as a tornado producing storm system. These storm systems emit infrasound (acoustic signals below human hearing, <20 Hz) up to 2 hours before tornadogenesis. Due to an acoustic ceiling and weak atmospheric absorption, infrasound can be detected from distances in excess of 300 miles. Thus infrasound could be used for long-range, passive monitoring and detection of tornadogenesis as well as directing UAS resources to high-decision-value-information. To achieve this the infrasonic signals with and without severe storms must be understood. This presentation will report findings from the first CLOUD MAP field demonstration, which acquired infrasonic signals while simultaneously sampling the atmosphere with UAS. Infrasonic spectra will be shown from a typical calm day, a continuous source (pulsed gas-combustion torch), singular events, and UAS flights as well as localization results from a controlled source and multiple microphones. This work was supported by NSF Grant 1539070: CLOUD MAP - Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics.

  19. Uncertainties associated with parameter estimation in atmospheric infrasound arrays

    NASA Astrophysics Data System (ADS)

    Szuberla, Curt A. L.; Olson, John V.

    2004-01-01

    This study describes a method for determining the statistical confidence in estimates of direction-of-arrival and trace velocity stemming from signals present in atmospheric infrasound data. It is assumed that the signal source is far enough removed from the infrasound sensor array that a plane-wave approximation holds, and that multipath and multiple source effects are not present. Propagation path and medium inhomogeneities are assumed not to be known at the time of signal detection, but the ensemble of time delays of signal arrivals between array sensor pairs is estimable and corrupted by uncorrelated Gaussian noise. The method results in a set of practical uncertainties that lend themselves to a geometric interpretation. Although quite general, this method is intended for use by analysts interpreting data from atmospheric acoustic arrays, or those interested in designing and deploying them. The method is applied to infrasound arrays typical of those deployed as a part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization.

  20. Infrasound workshop for CTBT monitoring: Proceedings

    SciTech Connect

    Christie, D.; Whitaker, R.

    1998-11-01

    It is expected that the establishment of new infrasound stations in the global IMS network by the Provisional Technical Secretariat of the CTBTO in Vienna will commence in the middle of 1998. Thus, decisions on the final operational design for IMS infrasound stations will have to be made within the next 12 months. Though many of the basic design problems have been resolved, it is clear that further work needs to be carried out during the coming year to ensure that IMS infrasound stations will operate with maximum capability in accord with the specifications determined during the May 1997 PrepCom Meeting. Some of the papers presented at the Workshop suggest that it may be difficult to design a four-element infrasound array station that will reliably detect and locate infrasound signals at all frequencies in the specified range from 0.02 to 4.0 Hz in all noise environments. Hence, if the basic design of an infrasound array is restricted to four array elements, the final optimized design may be suited only to the detection and location of signals in a more limited pass-band. Several participants have also noted that the reliable discrimination of infrasound signals could be quite difficult if the detection system leads to signal distortion. Thus, it has been emphasized that the detection system should not, if possible, compromise signal fidelity. This report contains the workshop agenda, a list of participants, and abstracts and viewgraphs from each presentation.

  1. Infrasound Detection of Large Mining Blasts in Kazakstan

    NASA Astrophysics Data System (ADS)

    Hagerty, M. T.; Kim, W.-Y.; Martysevich, P.

    - We describe infrasonic observations recorded since October, 1997, at the Kurchatov Observatory in Kazakstan from large mining blasts in Kazakstan and Siberia. Seismic signals are regularly recorded on a 21-element cross-array from events located at the Ekibastuz mine, 250km NW of Kurchatov. However, associated infrasonic detections are infrequent and appear to be seasonal, with maximum numbers of detections occurring during November to January. Raytracing through model atmosphere temperature and wind profiles predicts enhanced infrasound reception during the winter months, when the prevailing stratospheric winds blow towards Kurchatov. In addition, raytracing confirms that the first infrasound arrivals at Kurchatov propagate through the troposphere and are followed, some 50-70s later, by a stratospheric arrival.

  2. Infrasound propagation modelling using 4d atmospheric backgrounds

    NASA Astrophysics Data System (ADS)

    Streicher, Florian; Wuest, Sabine; Bittner, Michael

    2014-05-01

    Infrasound is very low frequency sound. Because of its low attenuation in the atmosphere, it is able to travel up to thousands of kilometers around the globe. A sound wave may cover a distance of about 1.000km within an hour. Sensors monitoring infrasound however can be some thousands of kilometers away from a specific source. For determining an infrasonic event, e.g. by the use of propagation modelling, with growing distance it is increasingly important to consider changes of the atmosphere in space and time. Most important and always accounted for in propagation modelling are changes of the atmosphere in vertical direction. Changes in horizontal direction generally are much smaller and sometimes are left away, e.g. for short distance calculations. Finally, changes in time hardly are considered. Effect and potential benefit of the use of 4d atmospheric specifications in infrasound propagation modelling are compared to 1d and 3d backgrounds, also taking into account selected atmospheric conditions and weather events. Differences in propagation on short and long distances are discussed. The results are based on HARPA/DLR.

  3. Progresses with Net-VISA on Global Infrasound Association

    NASA Astrophysics Data System (ADS)

    Mialle, Pierrick; Arora, Nimar

    2017-04-01

    Global Infrasound Association algorithms are an important area of active development at the International Data Centre (IDC). These algorithms play an important part of the automatic processing system for verification technologies. A key focus at the IDC is to enhance association and signal characterization methods by incorporating the identification of signals of interest and the optimization of the network detection threshold. The overall objective is to reduce the number of associated infrasound arrivals that are rejected from the automatic bulletins when generating the Reviewed Event Bulletins (REB), and hence reduce IDC analyst workload. Despite good accuracy by the IDC categorization, a number of signal detections due to clutter sources such as microbaroms or surf are built into events. In this work we aim to optimize the association criteria based on knowledge acquired by IDC in the last 6 years, and focus on the specificity of seismo-acoustic events. The resulting work has been incorporated into NETVISA [1], a Bayesian approach to network processing. The model that we propose is a fusion of seismic, hydroacoustic and infrasound processing built on a unified probabilistic framework. References: [1] NETVISA: Network Processing Vertically Integrated Seismic Analysis. N. S. Arora, S. Russell, and E. Sudderth. BSSA 2013

  4. Seismo-Acoustic Observations of Explosive Sources

    NASA Astrophysics Data System (ADS)

    Chael, E. P.; Hart, D. M.; Jones, K. R.

    2011-12-01

    Since January 2011, the Sandia National Laboratories Facility for Acceptance, Calibration and Testing (FACT) has operated a seismo-acoustic station with the purpose of recording local explosions on Kirtland Air Force Base (KAFB). Our immediate goals are to develop a catalog of events and a database of seismo-acoustic waveforms from ordnance disposal and Defense Threat Reduction Agency (DTRA) events. The catalog of events will include metadata such as shot time, size, type and location. The waveform archive includes a three-channel GS-13 seismometer and a single infrasound sensor (Chaparral 25 with 50' porous hose wind reduction system). In June of 2011 a weather station was added to complement the monitoring system by providing accurate wind conditions at the times of the explosive events. Monthly internal reports compiled by KAFB provided us with the metadata for the ordnance disposal explosions, and an agreement with DTRA has enabled us to obtain metadata on their events. To date 157 explosions have been identified, including 153 ordnance disposal events and 4 DTRA tests. Along with the catalog of events we have developed automated processing routines to extract both seismic and infrasound arrivals and measure basic waveform characteristics. These include amplitudes of pre-event noise, the direct seismic arrival, air-coupled seismic arrival, infrasound arrival, and wind speed/direction. Using the waveform measurements from the pre-event noise and air-coupled seismic arrival we calculate the SNR for the seismic component of the event. We also calculate the SNR for the infrasonic component of the event using pre-event noise and the direct infrasound arrival. Using the metadata and seismic and infrasonic SNR values we are able to calculate an air-to-ground coupling ratio for each event. For local (<10 km) explosion monitoring, the wind speed and direction can influence all of the analysis parameters. It will affect the pre-event noise level as well as the infrasound

  5. Infrasonic source location imaging with the USArray: Application to one year of seismic data

    NASA Astrophysics Data System (ADS)

    Walker, K. T.; Shelby, R.; Hedlin, M. A.; Degroot-Hedlin, C. D.

    2010-12-01

    The USArray directly measures ground motion, which can mostly be attributed to ocean waves, earthquakes, volcanoes, and weather systems that load the Earth’s surface. Another source of ground motion is the transfer of atmospheric acoustic energy into seismic energy at the Earth’s surface. Infrasound (low frequency sound below ~20 Hz) can travel great distances unattenuated in atmospheric ducts. The infrasonic wave field is rich due to a variety of anthropogenic and geophysical phenomena including earthquakes, volcanoes, landslides, meteors, lightning and sprites, auroras, and oceanic and atmospheric processes. Globally spaced microbarometer arrays with apertures of 100 m to 2 km are typically used to study these sources. However, these arrays are separated by thousands of kilometers, which places considerable limits on what they can teach us about infrasound source physics. The USArray is in a position to study infrasound sources in unprecedented detail. Here we apply reverse-time migration to acoustic-to-seismic coupled signals recorded by the USArray to detect and locate in two-dimensional space and time several hundred infrasound sources in the western U.S. that occurred during 2008. Each event is visually inspected and assigned a quality rating. Confidence regions are determined using a bootstrap technique. The highest quality signals can be observed out to at least 1500 km range. We report the source location parameters for these events and investigate detection and location patterns. These results suggest that seismic networks near nuclear test monitoring infrasound arrays could be used to reduce the false alarm rate by identifying nearby, repeating sources of infrasound that create signals that are detected by the infrasound arrays. More fundamentally, these detected events comprise a ground truth database that can be used to validate or improve atmospheric velocity models.

  6. The Chelyabinsk meteor: joint interpretation of infrasound, acoustic, and seismic waves (Invited)

    NASA Astrophysics Data System (ADS)

    Kitov, I. O.; Bobrov, D.; Rozhkov, M.

    2013-12-01

    The Chelyabinsk meteor was an event testing the capability of the International Monitoring System to measure and the International Data Centre to analyze sources similar to nuclear explosions. Monitoring of the Comprehensive Nuclear-Test-Ban Treaty suggests the possibility to detect infrasound (acoustic) and seismic signals from atmospheric and underground events and to locate their sources. The shock wave from the Chelyabinsk meteor generated an I-phase recorded by IMS infrasound stations and a series of seismic phases. The Pn-waves were observed by five near-regional seismic stations together with Sn- and Lg-waves. They are most likely associated with the impact of the meteor debris and the location associated with their source differs by tens of kilometers from that obtained by Rayleigh and Love waves. The latter were generated by acoustic (low-amplitude shock) waves hitting the ground beneath the trajectory of the meteor. Surprisingly, these surface waves associated with the meteor and observed at least at distances of 45 deg were not associated with the event in the Reviewed Event Bulletin. This implies a conceptual gap in the IDC processing and fusion of acoustic and seismic waves. We present an approximate distribution of energy release along the trajectory and thus the amplitude of the generated shock wave. It allows interpreting the period and amplitude dependence of the LR and LQ waves on the trajectory altitude. Corresponding relationships were obtained from the set of historical atmospheric nuclear tests. We also compare the Chelyabinsk meteor with seismic observations from the 1984 Chulym River (Siberia) bolide, which fell approximately 1000 km east of the studied event. We estimate the energy of both bodies and its distribution between various acoustic/seismic waves in order to interpret their respective sources and to discuss possible mechanisms of wave generation and conversion.

  7. Measurement and simulation of ground-coupled air waves and diffracted infrasound from the Kokoxili Earthquake, 14th Nov. 2001

    NASA Astrophysics Data System (ADS)

    Guilbert, J.; Le Pichon, A.; Vallee, M.; Alcoverro, B.; Ulziibat, M.

    2002-12-01

    On November 14, 2001, a strong earthquake measuring Mm 7.8 occurred in the Qinghai Province (China). Coherent infrasonic waves were detected during more than one hour by the IS34 infrasound station in Mongolia (~1500 km from the epicenter). Using an appropriate acoustic propagation model, the inversion of the infrasonic measurements allows a precise localization of the secondary sources distribution along the Qinghai mountains. The predominant source of infrasound is likely ground-coupled air waves generated by the strong variations of topography due to energy carried out by surface seismic waves that travel from the epicenter region through the Qinghai mountains. To confirm the locations of these distant source regions, the pressure field has been reconstructed at IS34. For each element of the topography, a synthetic seismogram used as an input of the integral relation of Huygens-Rayleigh permits to estimate the pressure variation. The synthetic pressure field fit the recorded data in azimuth and in relative amplitude. These results confirm the hypothesis of a strong coupling between the Rayleigh waves and the atmosphere, as it has already been observed during the Arequipa earthquake of June 23rd 2001. The simulations also permit to validate the infrasonic propagation model. This favorable setting within a region of high mountains makes easier the evaluation of the relative contribution of the different source mechanisms involved in large earthquake.

  8. Infrasound from lightning measured in Ivory Coast

    NASA Astrophysics Data System (ADS)

    Farges, T.; Matoza, R. S.

    2011-12-01

    It is well established that more than 2,000 thunderstorms occur continuously around the world and that about 45 lightning flashes are produced per second over the globe. More than two thirds (42) of the infrasound stations of the International Monitoring System (IMS) of the CTBTO (Comprehensive nuclear Test Ban Treaty Organisation) are now certified and routinely measure signals due to natural activity (e.g., airflow over mountains, aurora, microbaroms, surf, volcanoes, severe weather including lightning flashes, ...). Some of the IMS stations are located where worldwide lightning detection networks (e.g. WWLLN) have a weak detection capability but lightning activity is high (e.g. Africa, South America). These infrasound stations are well localised to study lightning flash activity and its disparity, which is a good proxy for global warming. Progress in infrasound array data processing over the past ten years makes such lightning studies possible. For example, Farges and Blanc (2010) show clearly that it is possible to measure lightning infrasound from thunderstorms within a range of distances from the infrasound station. Infrasound from lightning can be detected when the thunderstorm is within about 75 km from the station. The motion of the squall zone is very well measured inside this zone. Up to 25% of lightning flashes can be detected with this technique, giving better results locally than worldwide lightning detection networks. An IMS infrasound station has been installed in Ivory Coast for 8 years. The optical space-based instrument OTD measured a rate of 10-20 flashes/km^2/year in that country and showed strong seasonal variations (Christian et al., 2003). Ivory Coast is therefore a good place to study infrasound data associated with lightning activity and its temporal variation. First statistical results will be presented in this paper based on 3 years of data (2005-2008).

  9. The Effects of High Level Infrasound

    DTIC Science & Technology

    1980-02-01

    Ohreshold of such effects may be as low as 150 dl] for the chinchillas . .’The chinchilla is prob.ably more sensitive to infrasound than humans. There...several minutes (7 Hz). For these short times, no damage to the tympanic membrane or middle ear system occurred. However, the chinchilla results do...Johnson, D. L., "Exposure of Four Chinchillas to Infrasound," Research Memo dated Mar 1976, AMRL, WPAFB OH. 8. Tonndorf, J., "The Influence of Service on

  10. Automated detection and cataloging of global explosive volcanism using the International Monitoring System infrasound network

    NASA Astrophysics Data System (ADS)

    Matoza, Robin S.; Green, David N.; Le Pichon, Alexis; Shearer, Peter M.; Fee, David; Mialle, Pierrick; Ceranna, Lars

    2017-04-01

    We experiment with a new method to search systematically through multiyear data from the International Monitoring System (IMS) infrasound network to identify explosive volcanic eruption signals originating anywhere on Earth. Detecting, quantifying, and cataloging the global occurrence of explosive volcanism helps toward several goals in Earth sciences and has direct applications in volcanic hazard mitigation. We combine infrasound signal association across multiple stations with source location using a brute-force, grid-search, cross-bearings approach. The algorithm corrects for a background prior rate of coherent unwanted infrasound signals (clutter) in a global grid, without needing to screen array processing detection lists from individual stations prior to association. We develop the algorithm using case studies of explosive eruptions: 2008 Kasatochi, Alaska; 2009 Sarychev Peak, Kurile Islands; and 2010 Eyjafjallajökull, Iceland. We apply the method to global IMS infrasound data from 2005-2010 to construct a preliminary acoustic catalog that emphasizes sustained explosive volcanic activity (long-duration signals or sequences of impulsive transients lasting hours to days). This work represents a step toward the goal of integrating IMS infrasound data products into global volcanic eruption early warning and notification systems. Additionally, a better understanding of volcanic signal detection and location with the IMS helps improve operational event detection, discrimination, and association capabilities.

  11. Detection of the Combined Seismic and Infrasound Fields at the USArray Transportable Array

    NASA Astrophysics Data System (ADS)

    de Groot-Hedlin, C. D.; Hedlin, M. A. H.

    2016-12-01

    Many geophysical events, of natural or anthropogenic origin, are significant sources of both seismic and infrasound signals. Routine detection and accurate location of sources that generate both signal types is a significant processing challenge. We have recently developed a novel `big data' method to detect and locate geophysical events using a dense sensor network. In this method, the stations are divided into a mesh of "triad" arrays, which each comprise three adjacent stations. Standard array processing methods are used at each triad to detect signals that are consistent with plane wave propagation. When a coherent signal is detected, its phase velocity and direction of propagation is computed using tau-p. Results from all triads with signal detections that are consistent with a common source are collectively used to automatically and rapidly provide an accurate estimate of the source's origin time and location. This method has proven highly effective at detecting weak sources of infrasound and seismic signals that were located within or near the 400-station USArray Transportable Array. Examination of contemporaneous seismic and infrasound event catalogs reveals a number of sources that generate both infrasound and seismic signals. Most of these are identified as anthropogenic, as they occur during regular working hours each week, however a few of the sources appear to have a natural origin.

  12. Finite-difference time-domain modeling of infrasound from pulsating auroras and comparison with recent experiments

    NASA Astrophysics Data System (ADS)

    de Larquier, S.; Pasko, V. P.; Stenbaek-Nielsen, H. C.; Wilson, C. R.; Olson, J. V.

    2009-12-01

    Atmospheric infrasonic waves are acoustic waves with frequencies ranging from 0.02 to 10 Hz, slightly higher than the acoustic cut-off frequency (approximately 0.032 Hz), but lower than the audible frequencies (typically 20 Hz-15 kHz) [e.g., Blanc, Ann. Geophys., 3, 673, 1985]. A number of natural events have been identified as generating atmospheric infrasound, such as volcanoes, tornadoes, avalanches, earthquakes [e.g., Bedard and Georges, Physics Today, S3, 32, 2000], ocean surfaces [e.g., Gossard and Hooke, Waves in the Atmosphere, Elsevier, 1975, Ch. 9], lightning [e.g., Assink et al., GRL, 35, L15802, 2008; Pasko, JGR, 114, D08205, 2009], or transient luminous events in the middle atmosphere termed sprites [e.g., Farges, Lightning: Principles, Instruments and Applications, H.D. Betz et al. (eds), Springer, 2009, Ch. 18]. The importance of infrasound studies has been emphasized in the past ten years from the Comprehensive Nuclear-Test-Ban Treaty verification perspective [e.g., Le Pichon et al., JGR, 114, D08112, 2009]. A proper understanding of infrasound propagation in the atmosphere is required for identification and classification of different infrasonic waves and their sources [Drob et al., JGR, 108, D21, 4680, 2003]. The goal of the present work is to provide a quantitative interpretation and explanation of infrasonic signatures from pulsating auroras reported recently by Wilson et al. [GRL, 32, L14810, 2005]. The infrasound signals observed with an infrasonic array at Fairbanks, Alaska had a mean amplitude of 0.05 Pa, a delay of about 5 minutes from the pulsating aurora, and an almost normal incidence on the ground plane [Wilson et al., 2005]. We employ a finite-difference time-domain (FDTD) model of infrasound propagation in a realistic atmosphere. We use the absorption model of infrasound introduced by Sutherland and Bass [J. Acoust. Soc. Am., 115, 1012, 2004]. Classical absorption mechanisms as well as molecular relaxation mechanisms are taken into

  13. Permanent Infrasound Monitoring of Active Volcanoes in Ecuador

    NASA Astrophysics Data System (ADS)

    Ruiz, M. C.; Yepes, H. A.; Steele, A.; Segovia, M.; Vaca, S.; Cordova, A.; Enriquez, W.; Vaca, M.; Ramos, C.; Arrais, S.; Tapa, I.; Mejia, F.; Macias, C.

    2013-12-01

    Since 2006, infrasound monitoring has become a permanent tool for observing, analyzing and understanding volcanic activity in Ecuador. Within the framework of a cooperative project between the Japanese International Cooperation Agency (JICA) and the Instituto Geofísico to enhance volcano monitoring capabilities within the country, 10 infrasound sensors were deployed in conjunction with broadband seismic stations at Cotopaxi and Tungurahua volcanoes. Each station comprises 1 ACO microphone (model 7144) and an amplifier with a flat response down to 0.1 Hz. At Tungurahua, between July 2006 and July 2013, the network recorded more than 5,500 explosion events with peak-to-peak pressure amplitudes larger than 45 Pa at station Mason (BMAS) which is located ~ 5.5 km from the active crater. This includes 3 explosions with pressure amplitudes larger than 1,000 Pa and which all have exhibited clear shock wave components. Two seismic and infrasound arrays were also installed in 2006 under the Acoustic Surveillance for Hazardous Eruptions (ASHE) project, used in volcano monitoring at Tungurahua, Sangay, and Reventador. This venture was led by the Geological Survey of Canada and the University of Hawaii. Through the SENESCYT-IGEPN project, the Instituto Geofísico is currently installing a regional network of MB2005 microbarometers with the aim to enhance monitoring of active and potentially active volcanoes that include Reventador, Guagua Pichincha, Chimborazo, Antisana, Sangay, and Volcán Chico in the Galapagos Islands. Through the infrasound monitoring station at Volcán Chico it is also possible to extend observations to any activity initiated from Sierra Negra, Fernandina, Cerro Azul, and Alcedo volcanoes. During the past decade, a series of temporary acoustic arrays have also been deployed around Ecuador's most active volcanoes, helping to aid in short term volcanic monitoring and/or used in a series of research projects aimed at better understanding volcanic systems

  14. Regional measurements of infrasound signals from ARIANE-5 engine tests in Southern Germany

    NASA Astrophysics Data System (ADS)

    Koch, K.

    2012-04-01

    A well-controlled source of repetitive infrasound emissions was previously identified and has been related to development and acceptance tests of the European Space Agencies ARIANE-5 main engine. The propulsion testing facility of the German Aerospace Agency (DLR) near Heilbronn, Southern Germany, is a distance of about 320 km away from the International Monitoring System (IMS) station IS26 in east-southeasterly direction. In the past, signals associated with these propulsion tests could normally be detected at IS26 during winter months, but not during summer months, reflecting the changes in atmospheric conditions between winter and summer. Over the last year, DLR has prepared to conduct a series of seven propulsion tests which started in November 2011; with interim times between tests of 3-4 weeks it will last until late March or early April 2012. With mobile infrasound recording equipment available at BGR we planned to record the infrasonic wavefield along the path to IS26 at regular distances starting as close as 20 km from the source. Our aim is to study sound propagation from direct paths mainly involving the tropospheric layer through the "zone of silence" to distances close to IS26, where paths through stratospheric layers are followed. Preliminary results show that during the relevant winter season direct path propagation can be observed to some 40 km from the propulsion test source, even at seismographic stations where the acoustic wave couples into the ground. The tests are also observed at IS26, and waveform duration and f-k-analysis confirm the signals to be associated with the GT-type propulsion tests.

  15. Large meteoroid detection using the global IMS infrasound system

    SciTech Connect

    ReVelle, D. O.

    2002-01-01

    Numerous signals will be routinely detected using the 60 array, global IMS (International Monitoring System) infrasound network. Infrasonic signals are sub-audible quasi longitudinal, atmospheric waves in the frequency band from about 10 Hz to -5 minutes in period (limited by human acoustic audibility in the high frequency limit and by the wave-guide acoustic cut-off frequency and the Brunt Vaisalla frequency in the low frequency limit) These small amplitude waves are a natural subset of the well-known atmospheric acoustic-gravity wave regime which has been identified from the linearized equations of geophysical fluid mechanics in the flat earth approximation, neglecting the earth's rotation, etc. For the IMS network the instrumental pressure sensor response was chosen to range from -4 to 0.02 Hz. These are ground-based arrays of typically 4 to 9 sensors with separations of about 1-2 km between the array elements. Examples of naturally occurring impulsive sources of infrasound include volcanic eruptions, earthquakes, bolides (large meteor-fireballs entering the atmospheric at very high speeds up to -300 times faster than ground-level sound waves), microbaroms (the 'voice of the sea' due to the interaction of atmospheric storms and surface ocean waves) and the supersonic motion of the auroral electrojet at about 100 km altitude (auroral infrasonic waves), etc. In this paper we will briefly summarize our current state of knowledge of infrasound signals from bolides. This summary will include the generation of the signals at the complex, quasi-cylindrical line source, to the refraction and diffraction of the propagating waves by the middle atmospheric and tropospheric temperature and wind systems and finally, the detection of the signals and their interpretation by inferring the source properties, Le., source altitude, blast radius (see below) and the source energy, etc. In addition, we will use infrasound from energetic bolides to estimate the expected steady state

  16. Infrasound induced instability by modulation of condensation process in the atmosphere.

    PubMed

    Naugolnykh, Konstantin; Rybak, Samuil

    2008-12-01

    A sound wave in supersaturated water vapor can modulate both the process of heat release caused by condensation, and subsequently, as a result, the resonance interaction of sound with the modulated heat release provides sound amplification. High-intensity atmospheric perturbations such as cyclones and thunderstorms generate infrasound, which is detectable at large distances from the source. The wave-condensation instability can lead to variation in the level of infrasound radiation by a developing cyclone, and this can be as a precursor of these intense atmospheric events.

  17. Upper atmospheric processes as measured by collocated Lidar, infrasound, radiometer and airglow measurements

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Blanc, E.; Assink, J. D.; Ceranna, L.; Pilger, C.; Ross, O.; Keckhut, P.; Hauchecorne, A.; Schmidt, C.; Bittner, M.; Wuest, S.; Rüfenacht, R.; Kaempfer, N.; Smets, P.

    2013-12-01

    To better initialize weather forecasting systems, a key challenge is to understand stratosphere-resolving climate models. The ARISE project (http://arise-project.eu/) aims to design a novel infrastructure integrating different atmospheric observation networks to accurately recover the vertical structure of the wind and temperature from the ground to the mesosphere. This network includes Lidar and mesospheric airglow observations, complemented by continuous infrasound measurements. Together with additional ground-based wind radar system, such complementary techniques help to better describe the interaction between atmospheric layers from the ground to the mesosphere and the influence of large scale waves on the atmospheric dynamics. Systematic comparisons between these observations and the ECMWF upper wind and temperature models (http://www.ecmwf.int/) have been performed at the OHP site (Haute-Provence Observatory, France). The main results are outlined below. - Systematic comparisons between Lidar soundings (NDACC, http://ndacc-lidar.org/) and ECMWF highlight differences increasing with altitude. Below 50 km altitude, differences are as large as 20°K. In average, the temperature appears to be overestimated by ~5 m/s in the stratosphere and underestimated by ~10 m/s in the mesopause. - Comparisons with collocated infrasound measurements provide additional useful integrated information about the structure of the stratospheric waveguide. Below 0.5 Hz, most infrasound signals originate from ocean swells in the North Atlantic region. As expected, since most long-range propagating signals travel in the stratospheric waveguide, improved detection capability occurs downwind. Deviations from this trend are either related to short time-scale variability of the atmosphere (e.g., large-scale planetary waves, stratospheric warming effects), or can be explained by changes in the nature of the source. We investigate possible correlation between unexpected propagation paths and

  18. Characterization of absorption and non-linear effects in infrasound propagation using an augmented Burgers' equation

    NASA Astrophysics Data System (ADS)

    Sabatini, R.; Bailly, C.; Marsden, O.; Gainville, O.

    2016-12-01

    The long-range atmospheric propagation of explosion-like waves of frequency in the infrasound range is investigated using non-linear ray theory. Simulations are performed for sources of increasing amplitude on rays up to the lower thermosphere and for distances of hundreds of kilometres. A study of the attenuation of the waveforms observed at ground level induced by both the classical mechanisms and the vibrational relaxation of the molecules comprising the atmospheric gas is carried out. The relative importance of classical absorption and vibrational relaxation along the typical atmospheric propagation trajectories is assessed. Non-linear effects are highlighted as well and particular emphasis is placed on their strong interaction with absorption phenomena. A detailed description of the propagation model and of the numerical algorithm used in this work is first reported. Results are then discussed and the importance of the different mechanisms is clarified.

  19. Reduction of infrasounds in machines with hydrostatic drive.

    PubMed

    Kudźma, Zygmunt; Stosiak, Michał

    2013-01-01

    Some hazards posed by the operation of hydraulic systems, connected with low-frequency vibrations and noise are presented. Special attention is focused on infrasounds. The sources of low-frequency vibrations and noise and ways of reducing them are indicated. An original solution ensuring the effective reduction of vibrations and noise in a wide frequency range, i.e., a wide-band damper of pressure fluctuations, also performing the function of an acoustic filter, is proposed. The effectiveness of the damper was confirmed by the results of laboratory tests and tests carried out on engineering machines working in real conditions.

  20. Responses of the ear to low frequency sounds, infrasound and wind turbines.

    PubMed

    Salt, Alec N; Hullar, Timothy E

    2010-09-01

    Infrasonic sounds are generated internally in the body (by respiration, heartbeat, coughing, etc) and by external sources, such as air conditioning systems, inside vehicles, some industrial processes and, now becoming increasingly prevalent, wind turbines. It is widely assumed that infrasound presented at an amplitude below what is audible has no influence on the ear. In this review, we consider possible ways that low frequency sounds, at levels that may or may not be heard, could influence the function of the ear. The inner ear has elaborate mechanisms to attenuate low frequency sound components before they are transmitted to the brain. The auditory portion of the ear, the cochlea, has two types of sensory cells, inner hair cells (IHC) and outer hair cells (OHC), of which the IHC are coupled to the afferent fibers that transmit "hearing" to the brain. The sensory stereocilia ("hairs") on the IHC are "fluid coupled" to mechanical stimuli, so their responses depend on stimulus velocity and their sensitivity decreases as sound frequency is lowered. In contrast, the OHC are directly coupled to mechanical stimuli, so their input remains greater than for IHC at low frequencies. At very low frequencies the OHC are stimulated by sounds at levels below those that are heard. Although the hair cells in other sensory structures such as the saccule may be tuned to infrasonic frequencies, auditory stimulus coupling to these structures is inefficient so that they are unlikely to be influenced by airborne infrasound. Structures that are involved in endolymph volume regulation are also known to be influenced by infrasound, but their sensitivity is also thought to be low. There are, however, abnormal states in which the ear becomes hypersensitive to infrasound. In most cases, the inner ear's responses to infrasound can be considered normal, but they could be associated with unfamiliar sensations or subtle changes in physiology. This raises the possibility that exposure to the

  1. Numerical modeling of infrasound propagation at very long distance

    NASA Astrophysics Data System (ADS)

    Piserchia, Pierre-Franck; Roche, Roger

    2004-05-01

    Compliance with the CTBT in the atmosphere will be monitored by a world-wide network of infrasound stations consisting of 60 stations equipped with microbarographs in order to measure small changes in the air pressure in the frequency range 0.02 to 4 Hz. They are characterized by a good sensitivity, and by a large dynamic. By the application of array techniques, it is possible to determine the direction of pressure pulses caused by small explosions in the atmosphere, as well as shock waves caused by supersonic aircraft or meteorites. To take into account the nonlinear phenomena at the source and during the propagation, we are developing a numerical approach to solve the Euler nonlinear equation. In a first step, in the linear domain, this method is compared with two other numerical modeling approaches based on the ray tracing technique and the parabolic approach. In our test case, the source is on the ground and generates a 1-Pa pressure pulse centered at the frequency of 0.1 Hz. We considered an infrasound propagation over a distance of 500 km and an atmosphere height of 200 km. In a further step, the source level will be increased to study nonlinear phenomena.

  2. Infrasound from lightning measured in Ivory Coast

    NASA Astrophysics Data System (ADS)

    Farges, T.; Millet, C.; Matoza, R. S.

    2012-04-01

    It is well established that more than 2,000 thunderstorms occur continuously around the world and that about 45 lightning flashes are produced per second over the globe. More than two thirds (42) of the infrasound stations of the International Monitoring System (IMS) of the CTBTO (Comprehensive nuclear Test Ban Treaty Organisation) are now certified and routinely measure signals due to natural activity (e.g., airflow over mountains, aurora, microbaroms, surf, volcanoes, severe weather including lightning flashes, …). Some of the IMS stations are located where worldwide lightning detection networks (e.g. WWLLN) have a weak detection capability but lightning activity is high (e.g. Africa, South America). These infrasound stations are well localised to study lightning flash activity and its disparity, which is a good proxy for global warming. Progress in infrasound array data processing over the past ten years makes such lightning studies possible. For example, Farges and Blanc (2010) show clearly that it is possible to measure lightning infrasound from thunderstorms within a range of distances from the infrasound station. Infrasound from lightning can be detected when the thunderstorm is within about 75 km from the station. The motion of the squall zone is very well measured inside this zone. Up to 25% of lightning flashes can be detected with this technique, giving better results locally than worldwide lightning detection networks. An IMS infrasound station has been installed in Ivory Coast for 9 years. The lightning rate of this region is 10-20 flashes/km2/year from space-based instrument OTD (Christian et al., 2003). Ivory Coast is therefore a good place to study infrasound data associated with lightning activity and its temporal variation. First statistical results will be presented in this paper based on 4 years of data (2005-2009). For short lightning distances (less than 20 km), up to 60 % of lightning detected by WWLLN has been one-to-one correlated

  3. Can expectations produce symptoms from infrasound associated with wind turbines?

    PubMed

    Crichton, Fiona; Dodd, George; Schmid, Gian; Gamble, Greg; Petrie, Keith J

    2014-04-01

    The development of new wind farms in many parts of the world has been thwarted by public concern that subaudible sound (infrasound) generated by wind turbines causes adverse health effects. Although the scientific evidence does not support a direct pathophysiological link between infrasound and health complaints, there is a body of lay information suggesting a link between infrasound exposure and health effects. This study tested the potential for such information to create symptom expectations, thereby providing a possible pathway for symptom reporting. A sham-controlled double-blind provocation study, in which participants were exposed to 10 min of infrasound and 10 min of sham infrasound, was conducted. Fifty-four participants were randomized to high- or low-expectancy groups and presented audiovisual information, integrating material from the Internet, designed to invoke either high or low expectations that exposure to infrasound causes specified symptoms. High-expectancy participants reported significant increases, from preexposure assessment, in the number and intensity of symptoms experienced during exposure to both infrasound and sham infrasound. There were no symptomatic changes in the low-expectancy group. Healthy volunteers, when given information about the expected physiological effect of infrasound, reported symptoms that aligned with that information, during exposure to both infrasound and sham infrasound. Symptom expectations were created by viewing information readily available on the Internet, indicating the potential for symptom expectations to be created outside of the laboratory, in real world settings. Results suggest psychological expectations could explain the link between wind turbine exposure and health complaints.

  4. The effects of high level infrasound

    SciTech Connect

    Johnson, D.L.

    1980-02-01

    This paper will attempt to survey the current knowledge on the effects of relative high levels of infrasound on humans. While this conference is concerned mainly about hearing, some discussion of other physiological effects is appropriate. Such discussion also serves to highlight a basic question, 'Is hearing the main concern of infrasound and low frequency exposure, or is there a more sensitive mechanism'. It would be comforting to know that the focal point of this conference is indeed the most important concern. Therefore, besides hearing loss and auditory threshold of infrasonic and low frequency exposure, four other effects will be provided. These are performance, respiration, annoyance, and vibration.

  5. Infrasound from the September 24 2002 Vitim (Siberian) fireball

    NASA Astrophysics Data System (ADS)

    Shumilov, O. I.; Kasatkina, E. A.; Tereshchenko, E. D.; Kulichkov, S. N.; Raspopov, O. M.; Vasiljev, A. N.; Struev, A. G.

    2003-04-01

    On 24 September 2002, sensors aboard US Department Of Defence satellites detected the impact of a fireball at 16.49 UT near Bodaibo in Siberia (58.21 N, 113.46 E). Eyewitnesses described the fireball as a large bright star streaking across the sky, ending in bright flash and loud explosive noise. Ground shaking detonations were felt at a large distance (tens of kilometers). An array of microbarographs operated at Polar Geophysical Institute (PGI), Apatity (67.3 N, 33.3 E) recorded a pressure impulse with an amplitude of 45 dyn/cm^2 on September 24, 2002 at 22.20 UT, at a distance about of 4000 km from a fireball detection. The PGI microbarograph array consists of three spatially placed infrasound detectors for measurements of atmospheric waves in the frequency band of 0.0001 - 1 Hz. The computer-aided system permits to get information with a frequency of five times per second. The time interval between the bolide observation and the detection of pressure impulse is consistent with an acoustic travel time from the location of fireball impact. Estimates were made of both the local infrasound velocity and the direction of arrival of the signal. These values are in agreement with the travel velocity and the south azimuth. Estimates of the fireball mass from the radiated energy value agree with mass estimates calculated from the blast wave theory. These results seem to suppose the propagation of the infrasound signal from the Vitim fireball through atmospheric acoustic wave guide. According to Brown et al. (Nature, V420, 294, 2002) estimations the Earth is hit on average annually by the Vitim-like meteorite. Collisions of large asteroids with our planet result in dramatic impacts that can lead to the Earth magnetic field reversals. This work was supported by EC (grant INTAS 97-31008) and RFBR (grant 01-05-64850).

  6. VLBI observations of 416 extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Morabito, D. D.; Niell, A. E.; Preston, R. A.; Linfield, R. P.; Wehrle, A. E.; Faulkner, J.

    1986-01-01

    The Deep Space Network is establishing a high-accuracy Very Long Base Interferometry (VLBI) celestial reference frame. Presented are the VLBI results of observations of 416 radio sources with declination north of -45 degrees which were conducted at frequencies of 2.3 GHz and 8.4 GHz. At 2.3 GHz 323 of 391 radio sources observed were detected with a fringe spacing of 3 milliarcsec and a detection limit of approximately 0.1 Jy. At 8.4 GHz, 278 of 416 radio sources were detected with a fringe spacing of 1 milliarcsec and a detection limit of approximately 0.1 Jy. This survey was conducted primarily to determine the strength of compact components at 8.4 GHz for radio sources previously detected with VLBI at 2.3 GHz. Compact extragalactic radio sources with strong correlated flux densities at both frequencies are used to form a high-accuracy reference frame.

  7. VLBI observations of 416 extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Morabito, D. D.; Niell, A. E.; Preston, R. A.; Linfield, R. P.; Wehrle, A. E.; Faulkner, J.

    1986-01-01

    Very long baseline interferometry (VLBI) observations of 416 radio sources with declinations north of -45 deg have been conducted at frequencies of 2.3 and 8.4 GHz. At 2.3 GHz, 323 of 391 radio sources observed were detected with a fringe spacing of 3 milliarcsec and a detection limit of about 0.1 Jy. At 8.4 GHz, 278 of 416 radio sources were detected with a fringe spacing of 1 milliarcsec and a detection limit of about 0.1 Jy. This survey was conducted primarily to determine the strength of compact components at 8.4 GHz for radio sources previously detected with VLBI at 2.3 GHz. Compact extragalactic radio sources with strong correlated flux densities at both frequencies are used to form a high-accuracy reference frame.

  8. Unraveling Structural Infrasound: understanding the science for persistent remote monitoring of critical infrastructure (Invited)

    NASA Astrophysics Data System (ADS)

    McKenna, S. M.; Diaz-Alvarez, H.; McComas, S.; Costley, D.; Whitlow, R. D.; Jordan, A. M.; Taylor, O.

    2013-12-01

    In 2006, the Engineer Research and Development Center (ERDC) began a program designed to meet the capability gap associated with remote assessment of critical infrastructure. This program addresses issues arising from the use of geophysical techniques to solve engineering problems through persistent monitoring of critical infrastructure using infrasound. In the original 2006-2009 study of a railroad bridge in Ft. Leonard Wood, MO, the fundamental modes of motion of the structure were detected at up to 30 km away, with atmospheric excitation deemed to be the source driver. Follow-on research focused on the mechanically driven modes excited by traffic, with directional acoustic emanations. The success of the Ft. Wood ambient excitation study resulted in several subsequent programs to push the boundaries of this new technique for standoff assessment, discussed herein. Detection of scour and river system health monitoring are serious problems for monitoring civil infrastructure, from both civilian and military perspectives. Knowledge of overall system behavior over time is crucial for assessment of bridge foundations and barge navigation. This research focuses on the same steel-truss bridge from the Ft. Wood study, and analyzes 3D and 2D substructure models coupled with the superstructure reaction loads to assess the modal deformations within the infrasound bandwidth and the correlation to scour of embedment material. The Urban infrasound program is infrasound modeling, data analysis, and sensor research leading to the detection, classification and localization of threat activities in complex propagation environments. Three seismo-acoustic arrays were deployed on rooftops across the Southern Methodist University campus in Dallas, Texas, to characterize the urban infrasound environment. Structural sources within 15 km of the arrays have been identified through signal processing and confirmed through acoustical models. Infrasound is also being studied as a means of

  9. Measurement of Infrasound from the Marine Environment

    DTIC Science & Technology

    2015-09-01

    heave, as measured by the sea surface spectrum, is shown to occupy a significant portion of the infrasound receive frequency band. Measurements were...taken with a microbarometer fielded on board a ship during an at- sea experiment. The collected sound pressure data shows the interference effects of...6 WIND AND OCEAN SURFACE ROUGHNESS .............................................................. 6 SEA SURFACE SPECTRUM

  10. Evolution of the CTBTO Infrasound Technology Roadmap

    NASA Astrophysics Data System (ADS)

    Garces, Milton; Haralabus, Georgios; Noack, Patrick; Grenard, Patrick

    2013-04-01

    The CTBTO's nuclear explosion monitoring program needs to maintain its effectiveness and ensure its long-term relevance to the verification regime. The aims of its Infrasound Technology Roadmap (ITR) are to (1) establish a clear way forwards in accordance with the overall CTBTO nuclear monitoring vision, (2) couple scientific work with technology management, and (3) build upon existing technological accomplishments and project them into near-future technical targets. This ITR has a time horizon of seven years, and its activities are closely aligned to the Provisional Technical Secretariat's Technology Foresight Program, which extends its perspective to 20+ years. Phase 1 of the Roadmap effort requested input from the international infrasound community through the Request for Contributions released on 15 November 2012 (RFC R1). A set of metrics were selected to lend fairness, accountability, and scientific integrity to the evaluation of technical topics. The RFC was an inclusive, participatory effort inviting individual scientists to identify and assess technologies and procedures that can be infused into the IMS to meet its monitoring requirements and help evolve technology to achieve a reliable, sustainable and trustworthy monitoring system. We received over 680 individual topic evaluations from 52 members of the international infrasound community, with a 93% response rate. We present the statistical results from our survey as well as the highlights of the draft Infrasound Technology Roadmap Document.

  11. Infrasound Signal Characteristics from Small Earthquakes

    DTIC Science & Technology

    2010-09-01

    by many groups, e.g., McKenna et al. (2007), Che et al. (2002), and Sorrells et al. (1997). These studies show that infrasound detections can be...L. Zoback, and D. D. Blackwell, Eds. Boulder, CO: Geol. Soc. Am. Sorrells , G. G., E. Herrin, and J. L. Bonner (1997). Construction of regional

  12. Infrasound Signal Characteristics from Small Earthquakes

    DTIC Science & Technology

    2011-09-01

    infrasound from surface explosions ( Sorrells et al., 1997; Che et al., 2002; and McKenna et al., 2007) with the work identifying the importance of path...M. L., Blackwell, and D. D., Eds., Geological Society of America, Boulder, CO, pp. 185–228. Sorrells , G. G., E. Herrin, and J. L. Bonner (1997

  13. Infrasound Signals from Ground-Motion Sources

    DTIC Science & Technology

    2008-09-01

    piston. Let the piston displacement be given by z = Asin(2π ft) , (11) where A is the amplitude of the motion, f is frequency, and t is time...13) can be rewritten as (for the maximum value) p(h) = ρcAa2y = 2π 2Aρ f 2R2 h . (17) Evaluation then requires only the displacement...nuclear explosion, Amparo Corporation report (unpublished). 2008 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies 920

  14. Microseism Source Distribution Observed from Ireland

    NASA Astrophysics Data System (ADS)

    Craig, David; Bean, Chris; Donne, Sarah; Le Pape, Florian; Möllhoff, Martin

    2017-04-01

    Ocean generated microseisms (OGM) are recorded globally with similar spectral features observed everywhere. The generation mechanism for OGM and their subsequent propagation to continental regions has led to their use as a proxy for sea-state characteristics. Also many modern seismological methods make use of OGM signals. For example, the Earth's crust and upper mantle can be imaged using ``ambient noise tomography``. For many of these methods an understanding of the source distribution is necessary to properly interpret the results. OGM recorded on near coastal seismometers are known to be related to the local ocean wavefield. However, contributions from more distant sources may also be present. This is significant for studies attempting to use OGM as a proxy for sea-state characteristics such as significant wave height. Ireland has a highly energetic ocean wave climate and is close to one of the major source regions for OGM. This provides an ideal location to study an OGM source region in detail. Here we present the source distribution observed from seismic arrays in Ireland. The region is shown to consist of several individual source areas. These source areas show some frequency dependence and generally occur at or near the continental shelf edge. We also show some preliminary results from an off-shore OBS network to the North-West of Ireland. The OBS network includes instruments on either side of the shelf and should help interpret the array observations.

  15. Infrared Astronomy. [observations of extragalactic sources

    NASA Technical Reports Server (NTRS)

    Neugebauer, G.; Soifer, B. T.; Matthews, K.

    1981-01-01

    Several observational programs in infrared astronomy are described and significant findings are briefly discussed. The near infrared work concentrates largely on the use of the 5 m Hale telescope in spectroscopic and photometric studies of extragalactic sources. Observations of the P alpha line profile in a low redshift quasar, X-ray bursters, reflection nebula, and cataclysmic variables are included. Millimeter continuum observations of dust emission from quasars and galactic molecular clouds are also discussed. Finally, improvements to instrumentation are reported.

  16. Observations of water maser sources at Arcetri

    NASA Astrophysics Data System (ADS)

    Comoretto, Giovanni; Valdettaro, Riccardo; Palla, Francesco; Brand, Jan; Cesaroni, Riccardo; Felli, Marcello; Natale, Enzo; Palagi, Francesco; Panella, Dario; Tofani, Gianni

    We present the current activity of the Arcetri group in the field of water masers. This is mainly represented by observations with the Medicina radiotelescope, whose main outcome has been the compilation of the Arcetri Catalog and the study of time variability of selected sources. The Arcetri Catalog update reports the results of the observations carried out from January 1993 to April 2000 on a sample of 300 sources. The global properties of the complete Arcetri Catalog (including Comoretto et al. 1990, and Brand et al. 1994) are discussed. Of the 1013 sources, 937 have an IRAS counterpart within 1 arcmin from the nominal position of the maser. We establish a classification scheme based on the IRAS flux densities which allows to distinguish between water masers associated with star forming regions and late-type stars. The time variability study shows a large variety of behaviors. Generally more luminous sources present less variable emission and spectral components over a wider velocity range.

  17. Infrasound as a Detector of Local and Remote Turbulence

    NASA Astrophysics Data System (ADS)

    Cuxart, J.; Tatrai, D.; Weidinger, T.; Kircsi, A.; Józsa, J.; Kiss, M.

    2016-05-01

    Infrasound measurements are used to detect seismic waves and a large effort is devoted to eliminating the turbulence-related infrasound signal, usually considered as noise. Here we take a complementary approach, investigating whether infrasound can provide information on atmospheric turbulence. Microphone measurements of infrasound from an experimental campaign in Hungary in 2013 are used, together with data from a nearby sonic anemometer and a sodar. The comparison of infrasound integrated spectral energy to turbulent kinetic energy from the sonic provides a good match when turbulence is present near the ground. Moreover, on stable nights when the surface layer is strongly stratified and with turbulence absent, microphones sometimes recorded infrasound when the sodar showed a low-level jet above the surface inversion, indicating that microphones may be used as detectors of elevated turbulence.

  18. Inner Source Pickup Ions Observed by Ulysses

    NASA Astrophysics Data System (ADS)

    Gloeckler, G.

    2016-12-01

    The existence of an inner source of pickup ions close to the Sun was proposed in order to explain the unexpected discovery of C+ in the high-speed polar solar wind. Here I report on detailed analyses of the composition and the radial and latitudinal variations of inner source pickup ions measured with the Solar Wind Ion Composition Spectrometer on Ulysses from 1991 to 1998, approaching and during solar minimum. We find that the C+ intensity drops off with radial distance R as R-1.53, peaks at mid latitudes and drops to its lowest value in the ecliptic. Not only was C+ observed, but also N+, O+, Ne+, Na+, Mg+, Ar+, S+, K+, CH+, NH+, OH+, H2O+, H3O+, MgH+, HCN+, C2H4+, SO+ and many other singly-charged heavy ions and molecular ions. The measured velocity distributions of inner source pickup C+ and O+ indicate that these inner source pickup ions are most likely produced by charge exchange, photoionization and electron impact ionization of neutrals close to the Sun (within 10 to 30 solar radii). Possible causes for the unexpected latitudinal variations and the neutral source(s) producing the inner source pickup ions as well as plausible production mechanisms for inner source pickup ions will be discussed.

  19. Using the IMS infrasound network for the identification of mountain-associated waves and gravity waves hotspots

    NASA Astrophysics Data System (ADS)

    Hupe, Patrick; Ceranna, Lars; Pilger, Christoph; Le Pichon, Alexis

    2017-04-01

    The infrasound network of the International Monitoring System (IMS) has been established for monitoring the atmosphere to detect violations of the Comprehensive nuclear-Test-Ban Treaty (CTBT). The IMS comprises 49 certified infrasound stations which are globally distributed. Each station provides data for up to 16 years. Due to the uniform distribution of the stations, the IMS infrasound network can be used to derive global information on atmospheric dynamics' features. This study focuses on mountain-associated waves (MAWs), i.e. acoustic waves in the frequency range between approximately 0.01 Hz and 0.05 Hz. MAWs can be detected in infrasound data by applying the Progressive Multi-Channel Correlation (PMCC) algorithm. As a result of triangulation, global hotspots of MAWs can be identified. Previous studies on gravity waves indicate that global hotspots of gravity waves are similar to those found for MAWs by using the PMCC algorithm. The objective of our study is an enhanced understanding of the excitation sources and of possible interactions between MAWs and gravity waves. Therefore, spatial and temporal correlation analyses will be performed. As a preceding step, we will present (seasonal) hotspots of MAWs as well as hotspots of gravity waves derived by the IMS infrasound network.

  20. Evaluation of infrasound signals from the shuttle Atlantis using a large seismic network.

    PubMed

    de Groot-Hedlin, Catherine D; Hedlin, Michael A H; Walker, Kristoffer T; Drob, Douglas P; Zumberge, Mark A

    2008-09-01

    Inclement weather in Florida forced the space shuttle "Atlantis" to land at Edwards Air Force Base in southern California on June 22, 2007, passing near three infrasound stations and several hundred seismic stations in northern Mexico, southern California, and Nevada. The high signal-to-noise ratio, broad receiver coverage, and Atlantis' positional information allow for the testing of infrasound propagation modeling capabilities through the atmosphere to regional distances. Shadow zones and arrival times are predicted by tracing rays that are launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model. The predictions and observations compare favorably over much of the study area for both atmospheric specifications. To the east of the shuttle trajectory, there were no detections beyond the primary acoustic carpet. Infrasound energy was detected hundreds of kilometers to the west and northwest (NW) of the shuttle trajectory, consistent with the predictions of ducting due to the westward summer-time stratospheric jet. Both atmospheric models predict alternating regions of high and low ensonifications to the NW. However, infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification, possibly due to uncertainties in stratospheric wind speeds.

  1. Infrasound from the El Paso super-bolide of October 9, 1997

    SciTech Connect

    ReVelle, D.O.; Whitaker, R.W.; Armstrong, W.T.

    1998-12-31

    During the noon hour on October 9, 1997 an extremely bright fireball ({approx}-21.5 in stellar magnitude putting it into the class of a super-bolide) was observed over western Texas with visual sightings from as far away as Arizona to northern Mexico and even in northern New Mexico over 300 miles away. This event produced tremendously loud sonic boom reports in the El Paso area. It was also detected locally by 4 seismometers which are part of a network of 5 seismic stations operated by the University of Texas at El Paso (UTEP). Subsequent investigations of the data from the six infrasound arrays used by LANL (Los Alamos National Laboratory) and operated for the DOE (Department of Energy) as a part of the CTB (Comprehensive Test Ban) Research and Development program for the IMS (International Monitoring System) showed the presence of an infrasonic signal from the proper direction at the correct time for this super-bolide from two of the six arrays. Both the seismic and infrasound recordings indicated that an explosion occurred in the atmosphere at source heights from 28--30 km, having its epicenter slightly to the northeast of Horizon City, Texas. The signal characteristics, analyzed from {approx}0.1 to 5.0 Hz, include a total duration of {approx}4 min (at Los Alamos, LA) to >{approx}5 min at Lajitas, Texas, TXAR, another CTB IMS array operated by E. Herrin at Southern Methodist University (SMU) for a source directed from LA toward {approx}171--180 deg and from TXAR of {approx}321-4 deg respectively from true north. The observed signal trace velocities (for the part of the recording with the highest cross-correlation) at LA ranged from 300--360 m/sec with a signal velocity of 0.30 {+-} 0.03 km/sec, implying a Stratospheric (S Type) ducted path. The dominant signal frequency at LA was from 0.20 to 0.80 Hz, with a peak near 0.3 Hz. These highly correlated signals at LA had a very large, peak to peak, maximum amplitude of 21.0 microbars (2.1 Pa). The analysis, using

  2. On infrasound generated by wind farms and its propagation in low-altitude tropospheric waveguides

    NASA Astrophysics Data System (ADS)

    Marcillo, Omar; Arrowsmith, Stephen; Blom, Philip; Jones, Kyle

    2015-10-01

    Infrasound from a 60-turbine wind farm was found to propagate to distances up to 90 km under nighttime atmospheric conditions. Four infrasound sensor arrays were deployed in central New Mexico in February 2014; three of these arrays captured infrasound from a large wind farm. The arrays were in a linear configuration oriented southeast with 13, 54, 90, and 126 km radial distances and azimuths of 166°, 119°, 113°, and 111° from the 60 1.6 MW turbine Red Mesa Wind Farm, Laguna Pueblo, New Mexico, USA. Peaks at a fundamental frequency slightly below 0.9 Hz and its harmonics characterize the spectrum of the detected infrasound. The generation of this signal is linked to the interaction of the blades, flow gradients, and the supporting tower. The production of wind-farm sound, its propagation, and detection at long distances can be related to the characteristics of the atmospheric boundary layer. First, under stable conditions, mostly occurring at night, winds are highly stratified, which enhances the production of thickness sound and the modulation of other higher-frequency wind turbine sounds. Second, nocturnal atmospheric conditions can create low-altitude waveguides (with altitudes on the order of hundreds of meters) allowing long-distance propagation. Third, night and early morning hours are characterized by reduced background atmospheric noise that enhances signal detectability. This work describes the characteristics of the infrasound from a quasi-continuous source with the potential for long-range propagation that could be used to monitor the lower part of the atmospheric boundary layer.

  3. Ground-coupled air waves and diffracted infrasound from the Arequipa earthquake of June 23, 2001

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Guilbert, J.; Vega, A.; Garcés, M.; Brachet, N.

    2002-09-01

    On June 23, 2001, a strong earthquake measuring Mw 8.4 occurred along the coast of south-central Peru. Coherent infrasonic waves were detected over a period of one hour by the IS08 infrasound station in Bolivia. Analysis of the ground-coupled air waves shows that the rupture propagated from the northwestern to the southeastern part of the fault with a rupture velocity of 3.3 km/s. The azimuth variation of the infrasonic waves is attributed to a distribution of secondary sources along the highest mountain ranges, which excite infrasonic waves that are diffracted to the ground. The predominant source of infrasound is likely distributed along the Andean Cordillera. Using the azimuth and arrival time determination, the horizontal scale size of the distant source regions of infrasonic waves is reconstructed over distances greater than 400 km.

  4. Spectrophotometric observations of Molonglo radio source identifications

    NASA Technical Reports Server (NTRS)

    Smith, H. E.; Burbidge, E. M.; Baldwin, J. A.; Tohline, J. E.; Wampler, E. J.; Hazard, C.; Murdoch, H. S.

    1977-01-01

    The paper presents spectrophotometric observations of 76 optical objects identified with radio sources from the MC2 and MC3 catalogs. Line intensities, equivalent widths, line widths, and optical spectral indices are presented for 44 objects confirmed as quasi-stellar objects. The statistical and physical properties of the Molonglo sample are briefly discussed.

  5. Spectrophotometric observations of Molonglo radio source identifications

    NASA Technical Reports Server (NTRS)

    Smith, H. E.; Burbidge, E. M.; Baldwin, J. A.; Tohline, J. E.; Wampler, E. J.; Hazard, C.; Murdoch, H. S.

    1977-01-01

    The paper presents spectrophotometric observations of 76 optical objects identified with radio sources from the MC2 and MC3 catalogs. Line intensities, equivalent widths, line widths, and optical spectral indices are presented for 44 objects confirmed as quasi-stellar objects. The statistical and physical properties of the Molonglo sample are briefly discussed.

  6. Long period seismicity and very long period infrasound driven by shallow magmatic degassing at Mount Pagan, Mariana Islands

    USGS Publications Warehouse

    Lyons, John; Haney, Matt; Werner, Cynthia A.; Kelly, Peter; Patrick, Matthew R.; Kern, Christoph; Trusdell, Frank A.

    2016-01-01

    Long period (LP) seismicity and very long period infrasound (iVLP) were recorded during continuous degassing from Mount Pagan, Mariana Islands, in July 2013 to January 2014. The frequency content of the LP and iVLP events and delay times between the two arrivals were remarkably stable and indicate nearly co-located sources. Using phase-weighted stacking over similar events to dampen noise, we find that the LP source centroid is located 60 m below and 180 m west of the summit vent. The moment tensor reveals a volumetric source modeled as resonance of a subhorizontal sill intersecting a dike. We model the seismoacoustic wavefields with a coupled earth-air 3-D finite difference code. The ratios of pressure to velocity measured at the infrasound arrays are an order of magnitude larger than the synthetic ratios, so the iVLP is not the result of LP energy transmitting into the atmosphere at its epicenter. Based on crater shape and dimensions determined by structure from motion, we model the iVLP as acoustic resonance of an exponential horn. The source of the continuous plume from gas analysis is shallow magmatic degassing, which repeatedly pressurized the dike-sill portion of the conduit over the 7 months of observation. Periodic gas release caused the geologically controlled sill to partially collapse and resonate, while venting of gas at the surface triggered resonance in the crater. LP degassing only accounts for ~12% of total degassing, indicating that most degassing is relatively aseismic and that multiple active pathways exist beneath the vent.

  7. Seismic generated infrasounds on Telluric Planets: Modeling and comparisons between Earth, Venus and Mars

    NASA Astrophysics Data System (ADS)

    Lognonne, P. H.; Rolland, L.; Karakostas, F. G.; Garcia, R.; Mimoun, D.; Banerdt, W. B.; Smrekar, S. E.

    2015-12-01

    Earth, Venus and Mars are all planets in which infrasounds can propagate and interact with the solid surface. This leads to infrasound generation for internal sources (e.g. quakes) and to seismic waves generations for atmospheric sources (e.g. meteor, impactor explosions, boundary layer turbulences). Both the atmospheric profile, surface density, atmospheric wind and viscous/attenuation processes are however greatly different, including major differences between Mars/Venus and Earth due to the CO2 molecular relaxation. We present modeling results and compare the seismic/acoustic coupling strength for Earth, Mars and Venus. This modeling is made through normal modes modelling for models integrating the interior, atmosphere, both with realistic attenuation (intrinsic Q for solid part, viscosity and molecular relaxation for the atmosphere). We complete these modeling, made for spherical structure, by integration of wind, assuming the later to be homogeneous at the scale of the infrasound wavelength. This allows us to compute either the Seismic normal modes (e.g. Rayleigh surface waves), or the acoustic or the atmospheric gravity modes. Comparisons are done, for either a seismic source or an atmospheric source, on the amplitude of expected signals as a function of distance and frequency. Effects of local time are integrated in the modeling. We illustrate the Rayleigh waves modelling by Earth data (for large quakes and volcanoes eruptions). For Venus, very large coupling can occur at resonance frequencies between the solid part and atmospheric part of the planet through infrasounds/Rayleigh waves coupling. If the atmosphere reduced the Q (quality coefficient) of Rayleigh waves in general, the atmosphere at these resonance soffers better propagation than Venus crust and increases their Q. For Mars, Rayleigh waves excitations by atmospheric burst is shown and discussed for the typical yield of impacts. The new data of the Nasa INSIGHT mission which carry both seismic and

  8. Infrasound and Seismic Recordings of a US Airstrike on an ISIS Car Bomb Factory on June 3, 2015

    NASA Astrophysics Data System (ADS)

    Aleqabi, G. I.; Ghalib, H. A. A.; Wysession, M. E.

    2015-12-01

    Concurrent infrasound and seismic records of a jet airstrike in Iraq are presented. Media reports stated that US jets carried out a large airstrike on June 3, 2015, just after midnight local time, that targeted and destroyed an ISIS car bomb factory in Hawija, Iraq, just south of the city of Kirkuk, Iraq. The resulting explosion was felt within Kirkuk and at other locations as far as 34 km away from the Hawija factory. Seismic broadband stations located in northern Iraq, at a distance of about 160 km, show clear simultaneous signals of infrasound waves on the seismometers as well as on collocated infrasound equipment. From an analysis of the body waves, the Pg to Lg time difference is nearly ~20 sec, with a back azimuth of 250o to 260o, which is consistent with explosion location. The time difference between the Pg and infrasound signals is just over 7 minutes, consistent with sound speed in the atmosphere. No clear Rg wave was observed. As was demonstrated by Aleqabi, Wysession, and Ghalib [2015, BSSA, in press], broadband seismic recordings are able to identify and distinguish between several different kinds of MOUT (military operations in urban terrain) and even determine the magnitudes of ordinance used in certain blasts. The addition of collocated infrasound equipment provides additional constraints that can be used in the analysis of the size and form of the MOUT.

  9. The Temporal Morphology of Infrasound Propagation

    DTIC Science & Technology

    2010-01-01

    that incorpo- ration of hybrid ground-to-space (G2S) enviromental specifications in numerical calculations of infrasound signal travel time and...valuable ground-truth information that can be 1 Space Science Division, Naval Research Laboratory, Washington, DC, USA. E-mail: douglas.drob...NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Research Laboratory,Space Science Division,4555

  10. Observations and Modeling for Source Characterization

    DTIC Science & Technology

    2011-02-25

    and in and around the Tijuana River plume before, during and after storm events. Data were collected in February and March of 2008 and 2009 for a...sensors. These sources include riverine inputs from the Tijuana River and two outfall plumes in the region. The UUVs were also deployed to observe...California NCOM) was used to provide boundary information to the plume resolving higher resolution mesh. For example, the Tijuana River mouth, two outfall

  11. Acoustic buffeting by infrasound in a low vibration facility

    NASA Astrophysics Data System (ADS)

    MacLeod, B. P.; Hoffman, J. E.; Burke, S. A.; Bonn, D. A.

    2016-09-01

    Measurement instruments and fabrication tools with spatial resolution on the atomic scale require facilities that mitigate the impact of vibration sources in the environment. One approach to protection from vibration in a building's foundation is to place the instrument on a massive inertia block, supported on pneumatic isolators. This opens the questions of whether or not a massive floating block is susceptible to acoustic forces, and how to mitigate the effects of any such acoustic buffeting. Here this is investigated with quantitative measurements of vibrations and sound pressure, together with finite element modeling. It is shown that a particular concern, even in a facility with multiple acoustic enclosures, is the excitation of the lowest fundamental acoustic modes of the room by infrasound in the low tens of Hz range, and the efficient coupling of the fundamental room modes to a large inertia block centered in the room.

  12. Acoustic buffeting by infrasound in a low vibration facility.

    PubMed

    MacLeod, B P; Hoffman, J E; Burke, S A; Bonn, D A

    2016-09-01

    Measurement instruments and fabrication tools with spatial resolution on the atomic scale require facilities that mitigate the impact of vibration sources in the environment. One approach to protection from vibration in a building's foundation is to place the instrument on a massive inertia block, supported on pneumatic isolators. This opens the questions of whether or not a massive floating block is susceptible to acoustic forces, and how to mitigate the effects of any such acoustic buffeting. Here this is investigated with quantitative measurements of vibrations and sound pressure, together with finite element modeling. It is shown that a particular concern, even in a facility with multiple acoustic enclosures, is the excitation of the lowest fundamental acoustic modes of the room by infrasound in the low tens of Hz range, and the efficient coupling of the fundamental room modes to a large inertia block centered in the room.

  13. Infrasonic observations of the Northridge, California, earthquake

    SciTech Connect

    Mutschlecner, J.P.; Whitaker, R.W.

    1994-09-01

    Infrasonic waves from the Northridge, California, earthquake of 17 January 1994 were observed at the St. George, Utah, infrasound array of the Los Alamos National Laboratory. The distance to the epicenter was 543 kilometers. The signal shows a complex character with many peaks and a long duration. An interpretation is given in terms of several modes of signal propagation and generation including a seismic-acoustic secondary source mechanism. A number of signals from aftershocks are also observed.

  14. Infrasound production by bolides: A global statistical study

    NASA Astrophysics Data System (ADS)

    Ens, T. A.; Brown, P. G.; Edwards, W. N.; Silber, E. A.

    2012-05-01

    We have examined a dataset consisting of 71 bolides detected by satellite sensors, which provide energy and location estimates, with simultaneous measurements of the same events on 143 distinct waveforms. These bolides have total source energies ranging from 0.02 kt TNT equivalent yield to ≈20 kt and probable diameters of order a few meters on average. We find that it is possible to detect large events with energies of ≈20 kt or more globally. Infrasonic detections of these events for stratospheric arrivals have ranges between 350-17,000 km and show clear wind-related amplitude modifications. We find that our period-yield relations are virtually identical to that found from AFTAC nuclear test data with the most robust period-yield correlation found for those events having multiple station averaged periods. We have also found empirical expressions relating maximum expected detection range for infrasound as a function of energy and low and high frequency cut-off as a function of energy. Our multi-variate fits suggest that 1/2 > yield-scaling is most appropriate for long range bolide infrasound measurements with a distance scaling exponent of ≈1.1 best representing the data. Our best-fit wind correction exponent is a factor of ≈3 smaller than found by previous studies which we suggest may indicate a decrease in the value of k with range. We find that the integral acoustic efficiency for bolides is ≥0.01% with a best lower limit estimate nearer 0.1%. Finally, we conclude that a range independent atmosphere implementation of the normal-mode approach to simulate bolide amplitudes is ineffective at large ranges due to the large change in atmospheric conditions along source-receiver paths.

  15. Infrasound records from U.S. atmospheric tests

    SciTech Connect

    Chael, E.P.; Lohr, R.D.

    1998-07-01

    The United States conducted over 100 atmospheric nuclear tests at the Nevada Test Site from 1951 through 1962. Some of the earliest tests caused unexpected damage, primarily broken glass and cracked plaster, in Las Vegas and other surrounding communities. To address this problem, Sandia initiated a program to monitor and predict the pressure waves around NTS. Infrasound recording systems were developed, then field for all tests beginning with Operation Buster in October 1951. Investigators soon discovered that near-surface temperature inversions and wind profiles caused the damaging pressures in Las Vegas. A typical test was recorded at about a dozen stations from the Control Point on NTS to as far away as Pasadena, CA. In addition, some tests in the South Pacific were monitored, as well as numerous chemical explosions. Strip charts recorded signals in the frequency band from 0.05 to 30 Hz, and the paper tapes were achieved at Sandia in the early 1970s. The NTS events ranged in yield from below 1 ton to 74 kilotons; source altitudes varied from near ground level (including some cratering experiments) to as high as 11 km. The resulting data contain a wealth of information on the source function, yield scaling and regional propagation of infrasound signals from atmospheric explosions. The renewed interest in infrasonic monitoring for CTBT verification has prompted the authors to exhume some of the archived records. The authors plan to digitize the signals from several tests and evaluate their applicability to CTBT issues. In addition, they will collect any existing parametric measurements for these records (arrival times, amplitudes, etc.). All data will be converted to CSS database format and made available to the research community. If appropriate, the resulting information could also be included in the Knowledge Base under development for CTBT monitoring.

  16. Effects of topography and atmospheric structure on volcano infrasound

    NASA Astrophysics Data System (ADS)

    Marcillo, O. E.; Johnson, J. B.

    2009-12-01

    Proper interpretation of infrasonic waves produced by volcanic explosions requires understanding of weather and topographic effects. We have studied infrasound produced by two different volcanoes (Kilauea and Tungurahua) to determine the influence of topographic and atmospheric conditions on the infrasonic records corresponding to several weeks of eruptive activity. This analysis is necessary to understand and correct for phase and amplitude responses in order to properly perform waveform modeling. For instance, these corrections are necessary to obtain a better estimate of volume flux from the volcanic vent. The first case study is a dataset acquired during June of 2008 at Kilauea volcano in Hawaii, focused on the active Halemaumau Vent. Several days of infrasonic tremor were recorded by a 3-station infrasound network. These records show a strong influence of wind and topography in one of the three stations of the network. This station was located 2370 m from the vent, at a comparable distance to the other stations, but line of sight to the vent was obstructed by a 50-meter high crater edge, which introduced diffraction effects. Periods when wind blew in the vent-station direction are correlated with increase in infrasonic energy in the 0.5 - 1 Hz bandwidth. The second case focuses on a campaign conducted in June 2009 at Tungurahua Volcano, Ecuador. This study implemented two infrasonic arrays located on the flanks of the volcano 6000m north of the vent and on the flanks of an adjacent hill, 11,500m northeast. Compared to the proximal array a distinctive attenuation is evident at certain frequencies (0.5-1.5 Hz) at the distal array. This degree of attenuation is time-variant and is mostly likely related to changing atmospheric structure. An alternative explanation for the apparent spectral differences between near and far stations (and their evolution over time) is a complex (and changing) source geometry due to non-compact sources.

  17. Design of monitoring and early warning system for geo-hazards in Three Gorges reservoir area using infrasound

    NASA Astrophysics Data System (ADS)

    Qiu, N.; Zeng, Z. X.; Yang, Y. C.

    2009-04-01

    With the progress of the Three Gorges Dam Project, geological disasters have become increasingly prominent. The reservoir area prone to landslides, collapses, cracks, and earthquake disaster because the complex terrain and geological conditions. It is of significance to monitor and foresee geo-hazards in the reservoir area. Here we introduce our design of monitoring and early warning system for geo-hazards in Three Gorges reservoir area using infrasound. Infrasound may be abnormal during geological disasters, such as debris and earthquake occurred. The formation a d movement of debris flow in its basin will generate infrasound, and spread to the surrounding air medium. Velocity of infrasound is much larger than that of debris flow, so we can monitor and forecast debris flow using infrasound. The sudden vertical displacement brought about by earthquake will generate acoustic-gravity wave which can be observed in distance to monitor earthquake, especially to monitor earthquake precursors. So we try to monitor the geological disasters for the Three Gorges reservoir area in China by design a infrasound array monitor system. This work is supported by Chinese "985 Project". The infrasound monitor system is comprised of two observation stations arranged in Badong county inside the reservoir area and in Wuhan city, respectively. Each station has respectively arranged a kind of augmentable linear array in the form of quasi-uniform linear array and additional amending direction sensors. The linear array comprises eight sensors arranged in several different uniform intervals along a line. The amending direction sensor is situated at certain point in mid-perpendicular of linear array in order to reduce multiplicity in determine the direction of arrival. The sensors used in the system are CDC-2B capacitances infrasonic receiver which can observe frequency ranging 0~20Hz. The, measurement resolution is 750mV/LPa. Infrasonic wave signal collected by sensor is transferred from

  18. Detection of volcanic infrasound with a ring laser interferometer

    NASA Astrophysics Data System (ADS)

    Dunn, Robert W.; Hosman, Ashley R.

    2014-11-01

    Over the last 15 years, large horizontally mounted ring lasers have been used to study numerous geophysical phenomena. This paper provides examples of the sensitivity of large active ring laser interferometers to far field infrasound emissions from explosive volcanic eruptions. Volcanic infrasound is reported from representative eruptions of volcanoes Kelut (Kelud), Klyuchevskaya (Kliuchevskoi), Puyehua, Santa Maria, Sakurajima, and Tungurahua. The detected infrasound frequencies are in basic agreement with the far field air wave frequencies from the 1980 eruption of Mount St. Helens and the 1991 eruption of Mount Pinatubo. Cavities of large horizontally mounted active ring lasers contain two counter-propagating waves that in the presence Earth's rotation become traveling waves of slightly different frequencies. The Sagnac or beat frequency due to the difference in the traveling wave frequencies is modulated by geophysical phenomena, in this case volcanic infrasound. Signatures of the infrasound are found in the frequency modulated side bands.

  19. Locating industrial VOC sources with aircraft observations.

    PubMed

    Toscano, P; Gioli, B; Dugheri, S; Salvini, A; Matese, A; Bonacchi, A; Zaldei, A; Cupelli, V; Miglietta, F

    2011-05-01

    Observation and characterization of environmental pollution, focussing on Volatile Organic Compounds (VOCs), in a high-risk industrial area, are particularly important in order to provide indications on a safe level of exposure, indicate eventual priorities and advise on policy interventions. The aim of this study is to use the Solid Phase Micro Extraction (SPME) method to measure VOCs, directly coupled with atmospheric measurements taken on a small aircraft environmental platform, to evaluate and locate the presence of VOC emission sources in the Marghera industrial area. Lab analysis of collected SPME fibres and subsequent analysis of mass spectrum and chromatograms in Scan Mode allowed the detection of a wide range of VOCs. The combination of this information during the monitoring campaign allowed a model (Gaussian Plume) to be implemented that estimates the localization of emission sources on the ground.

  20. Infrasonic observations of the June 2009 Sarychev Peak eruption, Kuril Islands: Implications for infrasonic monitoring of remote explosive volcanism

    NASA Astrophysics Data System (ADS)

    Matoza, Robin S.; Le Pichon, Alexis; Vergoz, Julien; Herry, Pascal; Lalande, Jean-Marie; Lee, Hee-il; Che, Il-Young; Rybin, Alexander

    2011-02-01

    Sarychev Peak (SP), located on Ostrov Matua, Kurils, erupted explosively during 11-16 June 2009. Whereas remote seismic stations did not record the eruption, we report atmospheric infrasound (acoustic wave ~ 0.01-20 Hz) observations of the eruption at seven infrasound arrays located at ranges of ~ 640-6400 km from SP. The infrasound arrays consist of stations of the International Monitoring System global infrasound network and additional stations operated by the Korea Institute of Geoscience and Mineral Resources. Signals at the three closest recording stations IS44 (643 km, Petropavlovsk-Kamchatskiy, Kamchatka Krai, Russia), IS45 (1690 km, Ussuriysk, Russia), and IS30 (1774 km, Isumi, Japan) represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data (TERRA, NOAA, MTSAT). The eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data. Atmosphere-corrected infrasonic source locations determined from backazimuth cross-bearings of first-arrivals have a mean centroid ~ 15 km from the true location of SP. Scatter in source locations of up to ~ 100 km result from currently unresolved details of atmospheric propagation and source complexity. We observe systematic time-variations in trace-velocity, backazimuth deviation, and signal frequency content at IS44. Preliminary investigation of atmospheric propagation from SP to IS44 indicates that these variations can be attributed to solar tide variability in the thermosphere. It is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes. This study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the Kurils that have only sparse seismic network coverage.

  1. An Empirical Study of Atmospheric Correction Procedures for Regional Infrasound Amplitudes with Ground Truth.

    NASA Astrophysics Data System (ADS)

    Howard, J. E.

    2014-12-01

    This study focusses on improving methods of accounting for atmospheric effects on infrasound amplitudes observed on arrays at regional distances in the southwestern United States. Recordings at ranges of 150 to nearly 300 km from a repeating ground truth source of small HE explosions are used. The explosions range in actual weight from approximately 2000-4000 lbs. and are detonated year-round which provides signals for a wide range of atmospheric conditions. Three methods of correcting the observed amplitudes for atmospheric effects are investigated with the data set. The first corrects amplitudes for upper stratospheric wind as developed by Mutschlecner and Whitaker (1999) and uses the average wind speed between 45-55 km altitudes in the direction of propagation to derive an empirical correction formula. This approach was developed using large chemical and nuclear explosions and is tested with the smaller explosions for which shorter wavelengths cause the energy to be scattered by the smaller scale structure of the atmosphere. The second approach isa semi-empirical method using ray tracing to determine wind speed at ray turning heights where the wind estimates replace the wind values in the existing formula. Finally, parabolic equation (PE) modeling is used to predict the amplitudes at the arrays at 1 Hz. The PE amplitudes are compared to the observed amplitudes with a narrow band filter centered at 1 Hz. An analysis is performed of the conditions under which the empirical and semi-empirical methods fail and full wave methods must be used.

  2. Responses of the ear to low frequency sounds, infrasound and wind turbines

    PubMed Central

    Salt, Alec N.; Hullar, Timothy E.

    2010-01-01

    Infrasonic sounds are generated internally in the body (by respiration, heartbeat, coughing, etc) and by external sources, such as air conditioning systems, inside vehicles, some industrial processes and, now becoming increasingly prevalent, wind turbines. It is widely assumed that infrasound presented at an amplitude below what is audible has no influence on the ear. In this review, we consider possible ways that low frequency sounds, at levels that may or may not be heard, could influence the function of the ear. The inner ear has elaborate mechanisms to attenuate low frequency sound components before they are transmitted to the brain. The auditory portion of the ear, the cochlea, has two types of sensory cells, inner hair cells (IHC) and outer hair cells (OHC), of which the IHC are coupled to the afferent fibers that transmit “hearing” to the brain. The sensory stereocilia (“hairs”) on the IHC are “fluid coupled” to mechanical stimuli, so their responses depend on stimulus velocity and their sensitivity decreases as sound frequency is lowered. In contrast, the OHC are directly coupled to mechanical stimuli, so their input remains greater than for IHC at low frequencies. At very low frequencies the OHC are stimulated by sounds at levels below those that are heard. Although the hair cells in other sensory structures such as the saccule may be tuned to infrasonic frequencies, auditory stimulus coupling to these structures is inefficient so that they are unlikely to be influenced by airborne infrasound. Structures that are involved in endolymph volume regulation are also known to be influenced by infrasound, but their sensitivity is also thought to be low. There are, however, abnormal states in which the ear becomes hypersensitive to infrasound. In most cases, the inner ear’s responses to infrasound can be considered normal, but they could be associated with unfamiliar sensations or subtle changes in physiology. This raises the possibility that

  3. Infrasound of basaltic effusive activity at Piton de la Fournaise Volcano

    NASA Astrophysics Data System (ADS)

    Genco, Riccardo; Valade, Sebastien; Villeneuve, Nicolas; Peltier, Aline; Ferrazzini, Valérie; Di Muro, Andrea; Ripepe, Maurizio

    2016-04-01

    On August 24th 2015, a 67 days long eruptive activity started at Piton de la Fournaise Volcano. During the last phases of the eruption we deployed a portable, small aperture, infrasonic array which allowed us to record unprecedented data from effusive volcanic activity. The array consisted on four, few tens of meters spaced, infrasound pressure sensors and was installed on the outer rim of the Enclos Foqué, roughly 2.5 km far from the active vent, sited on the southern flank of the central cone. The system was almost continuously operating from October, 15th to December, 7th 2015, thus recording the end of the first eruptive phase (Autust 24th - October 17th) as well as the two short-living following phases (from 22 to 24 and from 29 to 31 October, 2015). The infrasound records have been coupled with discrete high-rate (30 Hz) thermal and visible imagery acquisitions located at a short distance from the vent (100-200 m) providing detailed information on the eruptive source dynamics. The comparison with seismic and ground tilt data recorded by the permanent network operated by the Observatoire Volcanologique du Piton de la Fournaise (OVPF), shows that infrasound can be succesfully used to locate the source, detect the onset, and the end, of the effusive phases as well as accurately track the time evolution of the effusive process. We present results which allows a detailed analysis of the shallow magma dynamics during the effusive activity at Piton de la Fournaise Volcano. As far as we know these are amongst the few rare infrasound dataset reported for this style of basaltic volcanic activity.

  4. On the infrasound detected from the 2013 and 2016 DPRK's underground nuclear tests

    NASA Astrophysics Data System (ADS)

    Assink, J. D.; Averbuch, G.; Smets, P. S. M.; Evers, L. G.

    2016-04-01

    The underground nuclear tests by the Democratic People's Republic of Korea (DPRK) generated atmospheric infrasound both in 2013 and 2016. Clear detections were made in the Russian Federation (I45RU) and Japan (I30JP) in 2013 at stations from the International Monitoring System. Both tropospheric and stratospheric refractions arrived at the stations. In 2016, only a weak return was potentially observed at I45RU. Data analysis and propagation modeling show that the noise level at the stations and the stratospheric circumpolar vortex were different in 2016 compared to 2013. As the seismic magnitude of the 2013 and 2016 nuclear test explosions was comparable, we hypothesize that the 2016 test occurred at least 1.5 times deeper. In such a case, less seismic energy would couple through the lithosphere-atmosphere interface, leading to less observable infrasound. Since explosion depth is difficult to estimate from seismic data alone, this motivates a synergy between seismics and infrasonics.

  5. Infrasound as a Depth Discriminant

    DTIC Science & Technology

    2010-09-01

    Technologies 659 Data Analysis An overall comparison of the detectability of shallow and deep earthquakes is given in Figure 3 (noting that this...acquisition of a high-quality dataset comprising both regional (Western US) and global components. An analysis of detectability highlights the fact that...identification through analysis of the variability of the repeating source. We discuss steps that are being taken to better constrain source, path, and

  6. IMS Seismic and Infrasound Stations Instrumental Challenges

    NASA Astrophysics Data System (ADS)

    Starovoit, Y. O.; Dricker, I. G.; Marty, J.

    2016-12-01

    The IMS seismic network is a set of monitoring facilities including 50 primary stations and 120 auxiliary stations. Besides the difference in the mode of data transmission to the IDC, technical specifications for seismographic equipment to be installed at both types of stations are essentially the same. The IMS infrasound network comprises 60 facilities with the requirement of continuous data transmission to IDC. The objective of this presentation is to report instrumental challenges associated with both seismic and infrasound technologies. In context of specifications for IMS seismic stations it was stressed that verification seismology is concerned with searching of reliable methods of signal detections at high frequencies. In the meantime MS/mb screening criteria between earthquakes and explosions relies on reliable detection of surface waves. The IMS seismic requirements for instrumental noise and operational range of data logger are defined as certain dB level below minimum background within the required frequency band from 0.02 to 16Hz. The type of sensors response is requested to be flat either in velocity or acceleration. The compliance with IMS specifications may thus introduce a challenging task when low-noise conditions have been recorded at the site. It means that as a station noise PSD approaches the NLNM it requires a high sensitive sensor to be connected to a quiet digitizer which may cause a quick system clip and waste of the available dynamic range. The experience has shown that hybrid frequency response of seismic sensors where combination of flat to velocity and flat to acceleration portions of the sensor frequency response may provide an optimal solution for utilization of the dynamic range and low digitizer noise floor. Vast efforts are also being undertaken and results achieved in the infrasound technology to standardize and optimize the response of the Wind-Noise Reduction System within the IMS infrasound passband from 0.02-4Hz and to deploy

  7. Impact of gravity waves on long-range infrasound propagation

    NASA Astrophysics Data System (ADS)

    Millet, Christophe; Lott, François; De La Camara, Alvaro

    2016-04-01

    In this work we study infrasound propagation in acoustic waveguides that support a finite number of propagating modes. We analyze the effects of gravity waves on these acoustic waveguides. Testing sound propagation in such perturbed fields can potentially be used to improve the gravity wave models. A linear solution modeling the interaction between an incoming acoustic wave and a randomly perturbed atmosphere is developed, using the forward-scattering approximation. The wave mode structure is determined by the effective sound speed profile which is strongly affected by gravity wave breaking. The random perturbations are described by a stochastic field predicted by a multiwave stochastic parameterization of gravity waves, which is operational in the LMDz climate model. The justification for this approach is two fold. On the one hand, the use of a few monochromatic waves mimics the observations of rather narrow-banded gravity wave packets in the lower stratosphere. On the other hand, the stochastic sampling of the gravity wave field and the random choice of wave properties deals with the inherent unpredictability of mesoscale dynamics from large scale conditions provided by the meteorological reanalysis. The transmitted acoustic signals contain a stable front and a small-amplitude incoherent coda. A general expression for the stable front is derived in terms of saddle-point contributions. The saddle-points are obtained from a WKB approximation of the vertical eigenvalue problem. This approach extract the dominant effects in the acoustic - gravity wave interaction. We present results that show how statistics of the transmitted signal are related to a few saddle-points and how the GW field can trigger large deviations in the acoustic signals. While some of the characteristics of the stable front can be directly related to that of a few individual gravity waves, it is shown that the amount of the launched gravity waves included in climate models can be estimated using

  8. Dust devil signatures in infrasound records of the International Monitoring System

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Christie, Douglas

    2015-03-01

    We explore whether dust devils have a recognizable signature in infrasound array records, since several Comprehensive Nuclear-Test-Ban Treaty verification stations conducting continuous measurements with microbarometers are in desert areas which see dust devils. The passage of dust devils (and other boundary layer vortices, whether dust laden or not) causes a local temporary drop in pressure: the high-pass time domain filtering in microbarometers results in a "heartbeat" signature, which we observe at the Warramunga station in Australia. We also observe a ~50 min pseudoperiodicity in the occurrence of these signatures and some higher-frequency infrasound. Dust devils do not significantly degrade the treaty verification capability. The pipe arrays for spatial averaging used in infrasound monitoring degrade the detection efficiency of small devils, but the long observation time may allow a useful census of large vortices, and thus, the high-sensitivity infrasonic array data from the monitoring network can be useful in studying columnar vortices in the lower atmosphere.

  9. Infrasound and seismic detections associated with the 7 September 2015 Bangkok fireball

    NASA Astrophysics Data System (ADS)

    Caudron, Corentin; Taisne, Benoit; Perttu, Anna; Garcés, Milton; Silber, Elizabeth A.; Mialle, Pierrick

    2016-12-01

    A bright fireball was reported at 01:43:35 UTC on September 7, 2015 at a height of ˜30 km above 14.5°N, 98.9°E near Bangkok, Thailand. It had a TNT yield equivalent of 3.9 kilotons (kt), making it the largest fireball detected in South-East Asia since the ˜50 kt 2009 Sumatra bolide. Infrasonic signals were observed at four infrasound arrays that are part of the International Monitoring System (IMS) and one infrasound array located in Singapore. Acoustic bearings and event origin times inferred from array processing are consistent with the eyewitness accounts. A seismic signal associated with this event was also likely recorded at station SRDT, in Thailand. An acoustic energy equivalent of 1.15 ± 0.24 kt is derived from the Singaporean acoustic data using the period of the peak energy.

  10. Infrasound and seismic detections associated with the 7 September 2015 Bangkok fireball

    SciTech Connect

    Caudron, Corentin; Taisne, Benoit; Perttu, Anna; Garces, Milton; Silber, Elizabeth A.; Mialle, Pierrick

    2016-08-22

    A bright fireball was reported at 01:43:35 UTC on September 7, 2015 at a height of ~30 km above 14.5°N, 98.9°E near Bangkok, Thailand. It had a TNT yield equivalent of 3.9 kilotons (kt), making it the largest fireball detected in South–East Asia since the ~50 kt 2009 Sumatra bolide. Infrasonic signals were observed at four infrasound arrays that are part of the International Monitoring System (IMS) and one infrasound array located in Singapore. Acoustic bearings and event origin times inferred from array processing are consistent with the eyewitness accounts. A seismic signal associated with this event was also likely recorded at station SRDT, in Thailand. As a result, an acoustic energy equivalent of 1.15 ± 0.24 kt is derived from the Singaporean acoustic data using the period of the peak energy.

  11. Infrasound and seismic detections associated with the 7 September 2015 Bangkok fireball

    DOE PAGES

    Caudron, Corentin; Taisne, Benoit; Perttu, Anna; ...

    2016-08-22

    A bright fireball was reported at 01:43:35 UTC on September 7, 2015 at a height of ~30 km above 14.5°N, 98.9°E near Bangkok, Thailand. It had a TNT yield equivalent of 3.9 kilotons (kt), making it the largest fireball detected in South–East Asia since the ~50 kt 2009 Sumatra bolide. Infrasonic signals were observed at four infrasound arrays that are part of the International Monitoring System (IMS) and one infrasound array located in Singapore. Acoustic bearings and event origin times inferred from array processing are consistent with the eyewitness accounts. A seismic signal associated with this event was also likelymore » recorded at station SRDT, in Thailand. As a result, an acoustic energy equivalent of 1.15 ± 0.24 kt is derived from the Singaporean acoustic data using the period of the peak energy.« less

  12. Frequency-wavenumber processing for infrasound distributed arrays.

    PubMed

    Costley, R Daniel; Frazier, W Garth; Dillion, Kevin; Picucci, Jennifer R; Williams, Jay E; McKenna, Mihan H

    2013-10-01

    The work described herein discusses the application of a frequency-wavenumber signal processing technique to signals from rectangular infrasound arrays for detection and estimation of the direction of travel of infrasound. Arrays of 100 sensors were arranged in square configurations with sensor spacing of 2 m. Wind noise data were collected at one site. Synthetic infrasound signals were superposed on top of the wind noise to determine the accuracy and sensitivity of the technique with respect to signal-to-noise ratio. The technique was then applied to an impulsive event recorded at a different site. Preliminary results demonstrated the feasibility of this approach.

  13. Regional Localization with the Hawaii Island Infrasound Network

    NASA Astrophysics Data System (ADS)

    Perttu, A. B.; Garces, M. A.; Thelen, W. A.

    2013-12-01

    The Big Island of Hawaii is home to an extensive network of infrasound arrays, with additional arrays in Maui and Kauai. Four of the six Hawaii arrays are focused on Kilauea volcano. This project examines several methods for estimating source location, onset time, duration, and source energetics from regional infrasonic signals, with an emphasis on improving signal characterization. Diverse persistent natural and anthropogenic regional sources provide a data set for addressing localization with the Hawaii network. Explosions at the Pohakuloa Training Area, rock falls within the Halema'uma'u vent, and a repetitive unknown signal off the coast of Maui supply transient signals with known and unknown locations. In addition, Halema'uma'u and Pu'u O'o vents both produce infrasonic tremor with known locations. Well-constrained signal discrimination and characterization is essential for good location results. This paper presents progress in signal processing, feature extraction, and event association with standardized, self-similar, logarithmic time-frequency multiresolution algorithms. The Infrasonic Energy, Nth Octave (INFERNO) energy estimation suite of Garces (2013) is used in conjunction with the PMCC4 array processing algorithm to extract standardized signal features and parameters for improved regional association, localization, and source characterization.

  14. Atmospheric infrasound propagation modelling using the reflectivity method with a direct formulation of the wind effect

    NASA Astrophysics Data System (ADS)

    Maupin, Valerie; Näsholm, Sven Peter; Schweitzer, Johannes; Gibbons, Steven J.

    2016-04-01

    We recently advocated using the reflectivity method, also known as the wavenumber integration method or fast-field program, to model atmospheric infrasound propagation at regional distances. The advantage of the reflectivity method is its ability to model the full wavefield, including diffractive effects with head waves and shadow zone arrivals, in a broad frequency range but still at a relatively low computational cost. Attenuation can easily be included, giving the possibility to analyse relative amplitudes and frequency content of the different arrivals. It has clear advantages compared with ray theory in terms of predicting phases considering the particular frequent occurrence of shadow zone arrivals in infrasound observations. Its main limitation, at least in the traditional form of the method, lies in the fact that it can only handle range-independent models. We presented earlier some reflectivity method simulations of an observed accidental explosion in Norway. Wind intensity and direction are non-negligible parameters for infrasound propagation and these are appropriately taken into account in most infrasound ray-tracing codes. On the other hand, in the previous reflectivity simulations wind was taken into account only through the effective sound speed approximation where the horizontal projection of the wind field is added to the adiabatic sound speed profiles. This approximation is appropriate for dominantly horizontal propagation but can give incorrect arrival times and shadow zone locations for waves which have a significant portion of their propagation path at more vertical incidence, like thermospheric arrivals. We present here how we have modified the original reflectivity algorithm in order to take the wind into account in a more correct fashion, and how this improvement influences the synthetics.

  15. Seismic and infrasound monitoring at Cotopaxi volcano

    NASA Astrophysics Data System (ADS)

    Ruiz, M.; Yepes, H.; Palacios, P.; Troncoso, L.; Mothes, P.; Kumagai, H.

    2012-04-01

    Cotopaxi is an active ice-capped volcano (5967m) located 60 km SE from Quito and is one of the largest and more hazardous volcanoes in the Northern Andes. Monitoring of Cotopaxi, using seismic and infrasound techniques has improving significantly since 1976, when three short-period stations were deployed temporarily in response to an increase of fumarolic activity. Later in May 1977, a short-period vertical seismometer was installed on the NW flank at 7 km from the crater. Since 1986 a short-period seismic station is working at the northern flank of Cotopaxi and transmitting analog data to the Instituto Geofisico. In 1993 a network of 4 short-period seismic stations were installed on all flanks of the volcano. Between March 1996 and June 1997 a temporal network of 16 stations were deployed for several months in order to study local seismicity and internal structure (Metaxian et al., 1999). Since 2006, a network of five broad band stations (0.02-60 s) and low-frequency infrasound sensors (0.01-10 s) were installed through a JICA Cooperation Project (Kumagai et al., 2007). Data is transmitted to the Instituto Geofisico via a digital radio system. Through this network, LP and VLP events have been recorded and analyzed (Molina et al., 2008). VLP events were located beneath the north and north-eastern flank using waveform inversion and amplitude distribution methods (Kumagai et al., 2010).

  16. Volcanic Infrasound - A technical topic communicated in an entertaining way

    NASA Astrophysics Data System (ADS)

    Kerlow, Isaac

    2017-04-01

    Volcanic Infrasound is a 9-minute film about using infrasound waves to detect and measure volcanic eruptions as they unfold. The film was made by an interdisciplinary team of filmmakers and scientists for a general audience. The movie explains the basic facts of using infrasound to detect volcanic activity, and it also shows volcano researchers as they install infrasound sensors in a natural reserve in the middle of the city. This is the first in a series of films that seek to address natural hazards of relevance to Singapore, a country shielded from violent hazards. This presentation reviews the science communication techniques and assumptions used to develop and produce this entertaining scientific documentary short. Trailer: https://vimeo.com/192206460

  17. ASTERIA: A Balloon-Borne Experiment for Infrasound Detection

    NASA Astrophysics Data System (ADS)

    Young, Eliot; Wahl, Kerry; Ballard, Courtney; Daugherty, Emily; Dullea, Connor; Garner, Kyle; Heaney, Martin; Thom, Ian; Von Hendy, Michael; Young, Emma; Diller, Jed; Dischner, Zach; Drob, Douglas; Boslough, Mark; Brown, Peter

    2015-04-01

    ASTERIA (Aloft Stratospheric Testbed for Experimental Research on Infrasonic Activity) is a small (<20 kg) payload designed to measure infrasound disturbances from a balloon-borne platform at altitudes near 60,000 ft (~20 km). A balloon platform is expected to have two advantages over ground-based infrasound stations: a relatively benign wind environment and exposure to higher signal strengths within a stratospheric duct. ASTERIA's nominal sensitivity requirements are to measure waves between 0.1 to 20 Hz at the 0.1 Pa level with signal-to-noise ratios of 5 or better. At the time of this writing, we have tested wave sensors based on the differential pressure transducers recently flown by Bowman et al. (2014) on a NASA/HASP (High Altitude Student Payload); our modified pressure sensor was tested in a NOAA piston-bellows facility in Boulder, CO. Our goal of characterizing 0.1 Pa amplitude waves requires that combined noise sources are below the the 0.02 Pa rms level. ASTERIA carries five differential transducers with port inlets arranged a diamond-like pattern (one zenith- and one nadir-facing port, plus three horizontal ports equally spaced in azimuth). Baffling for these sensors is a hybrid of perforated tubing and porous barriers, as described in Hedlin (2014). Other noise sources of concern include the electronic amplification of the transducer voltages and low-frequency pressure waves caused by pendulum or twisting modes of the payload. We will report on our plans to characterize and reduce these noise sources. The ASTERIA payload is intended to fly on long-duration super-pressure balloons for intervals of ~100 days. We plan to conduct an experiment in the summer or fall of 2015 in which a calibrated disturbance is set off and detected simultaneously from stratospheric ASTERIA payloads and ground-based stations. References: 1) Bowman et al. 2014, "Balloons over Volcanoes Scientific Report," HASP 2014 final report. 2) Hedlin 2003, "Infrasonic Wind-noise Reduction

  18. Balloon-Borne Infrasound Detection of Energetic Bolide Events

    NASA Astrophysics Data System (ADS)

    Young, Eliot F.; Ballard, Courtney; Klein, Viliam; Bowman, Daniel; Boslough, Mark

    2016-10-01

    Infrasound is usually defined as sound waves below 20 Hz, the nominal limit of human hearing. Infrasound waves propagate over vast distances through the Earth's atmosphere: the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization) has 48 installed infrasound-sensing stations around the world to detect nuclear detonations and other disturbances. In February 2013, several CTBTO infrasound stations detected infrasound signals from a large bolide that exploded over Chelyabinsk, Russia. Some stations recorded signals that had circumnavigated the Earth, over a day after the original event. The goal of this project is to improve upon the sensitivity of the CTBTO network by putting microphones on small, long-duration super-pressure balloons, with the overarching goal of studying the small end of the NEO population by using the Earth's atmosphere as a witness plate.A balloon-borne infrasound sensor is expected to have two advantages over ground-based stations: a lack of wind noise and a concentration of infrasound energy in the "stratospheric duct" between roughly 5 - 50 km altitude. To test these advantages, we have built a small balloon payload with five calibrated microphones. We plan to fly this payload on a NASA high-altitude balloon from Ft Sumner, NM in August 2016. We have arranged for three large explosions to take place in Socorro, NM while the balloon is aloft to assess the sensitivity of balloon-borne vs. ground-based infrasound sensors. We will report on the results from this test flight and the prospects for detecting/characterizing small bolides in the stratosphere.

  19. Can Gamma Ray Bursts be Detected Using Infrasound

    NASA Astrophysics Data System (ADS)

    Palmer, Jahi; McGruder, C.; Hetzer, C.

    2010-01-01

    CAN GAMMA RAY BURST BE DETECTED USING INFRASOUND Infrasound has been used to detect sonic disturbances in earth's atmosphere caused by terrestrial events such as earthquakes and lightning. It may be possible to detect celestial events such as Gamma Ray Bursts (GRB's) through this method. We have searched for GRB's which are known to have caused ionospheric disturbances in infrasonic data. None of the selected GRB's were found to be associated with infrasonic disturbances.

  20. Effects of fine-scale orography on infrasound propagation

    NASA Astrophysics Data System (ADS)

    Pilger, C.; Streicher, F.; Wüst, S.; Bittner, M.

    2012-04-01

    The sensitivity of infrasound propagation to reflections by a non-flat surface is investigated within this study. Infrasound propagation modelling is performed at the German Remote Sensing Data Center of the German Aerospace Center (DLR-DFD) using improved 3d ray-tracing methods (HARPA/DLR). Terrain information is newly included in the modelling using a high-resolution digital surface model. The SRTM30-PLUS digital surface model incorporates the DLR "Shuttle Radar Topography Mission" and complementary surface information to generate a global, equidistant and complete data set for surface orography. The maximum horizontal resolution is 30 arc seconds (about 1km), the maximum vertical resolution is 1m. The resolution of the model can be adapted to the wavelength of the considered infrasound signal. The orography is implemented as background data using bicubic spline interpolation and thus provides smooth surface layer information for infrasound propagation modelling. First modelling cases containing the European Alps region show that orography has a significant influence on infrasound propagation. Ducts and propagation patterns can be veritably changed according to reflection by non-flat fine-scale orography. First results on the sensitivity of infrasound propagation to surface orography will be presented.

  1. Large Bubble Growth Quantified By Video and Infrasound at Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Miller, A. J. C.; Johnson, J. B.

    2014-12-01

    Mount Erebus lava lake eruptions exhibit many characteristic strombolian attributes including the ascent of a large gas slug(s) through the magma column followed by its expansion and bursting at the surface. Strombolian explosions correspond to pressurized large (>10 m radius) bubbles, which distend the lava lake surface before bursting within a few tenths of a second thus generating infrasonic impulses followed by decaying oscillations. We quantify the dynamics of bubble evolution using infrasound and time synchronized video data recording at ~30 FPS. Video footage is used to synthesize pressure time series during eruptions assuming a simple acoustic source. These synthetic pressure records are directly compared to infrasound pressure records collected at two sites located ~300 m from the lava lake source. A scaled relationship exists between infrasound and video derived pressures where video generally overestimates the volumetrically expanding source. This scaling is due to the image processing routine, which tracks and models the ejection of ballistics during eruption as an expanding hemisphere and not necessarily the expansion of a translucent gas source that is not directly visible with optical imagery. Using both data sets, we describe Erebus lava lake eruptions in three phases with smooth distension of spherical cap (P1), followed by membrane fragmentation and violent gas expulsion (P2) and finally a contraction of the volumetric gas source due to an initial over-expansion followed by re-equilibration. (P3). Specifically, P3 is identified by decaying oscillations of the pressure record which has been well modeled in laboratory experiments but never described at Erebus.

  2. Reanalysis of large infrasound datasets with FLOWS

    NASA Astrophysics Data System (ADS)

    Mialle, P.; Millet, C.; Bertin, M.; Vergoz, J.

    2016-12-01

    While long-range infrasound propagation modeling is a useful tool in geophysics and nuclear treaty verification, the inherent unpredictability of subgrid-scale atmosphere dynamics results in a poorly constrained propagation medium and a large number of length scales. When faced with such a situation it is natural to treat incomplete knowledge within a probabilistic framework and to seek a numerical approach that describes long-range propagation at the lowest numerical cost and complexity. Such a task is rendered complex by the fact that each plausible atmospheric state produces large deviations from the operational numerical weather predictions. In this work, we pursue a new approach, in which propagation modeling is based on reduced-order models provided by the numerical platform FLOWS (Fast Low-Order Wave Simulation). The reduced models are obtained by retaining a few propagating modes, with the aim of simplifying the acoustic model to the point that the predicted statistics/sensitivities of signals are correct. In the atmosphere, these modes are confined within waveguides causing the sound to propagate through multiple paths to the receiver. FLOWS performance is demonstrated using several ground truth events registered by the International Monitoring System (IMS). By examining how the uncertainty manifests statistically within the waveforms, we will show how we can update the numerically obtained signals from a sequence of reduced models and how we can decide from modeling whether a recorded signal is plausible or not. In time, the use of FLOWS in combination with a bayesian approach should help the global infrasound association process.

  3. Comparing near-regional and local measurements of infrasound from Mount Erebus, Antarctica: Implications for monitoring

    NASA Astrophysics Data System (ADS)

    Dabrowa, A. L.; Green, D. N.; Johnson, J. B.; Phillips, J. C.; Rust, A. C.

    2014-11-01

    amplitude and lower atmosphere effective sound speed structure. At times of increased sound speed gradient, higher amplitude decay rates are observed, consistent with increased upward refraction of acoustic energy along the propagation path. This study indicates that whilst monitoring activity levels at near-regional ranges can be successful, variable amplitude decay rate means quantitative analysis of infrasound data for eruption intensity and magnitude is not advisable without the consideration of local atmospheric sound speed structure.

  4. Southwest U.S. Seismo-Acoustic Network: An Autonomous Data Aggregation, Detection, Localization and Ground-Truth Bulletin for the Infrasound Community

    NASA Astrophysics Data System (ADS)

    Jones, K. R.; Arrowsmith, S.

    2013-12-01

    The Southwest U.S. Seismo-Acoustic Network (SUSSAN) is a collaborative project designed to produce infrasound event detection bulletins for the infrasound community for research purposes. We are aggregating a large, unique, near real-time data set with available ground truth information from seismo-acoustic arrays across New Mexico, Utah, Nevada, California, Texas and Hawaii. The data are processed in near real-time (~ every 20 minutes) with detections being made on individual arrays and locations determined for networks of arrays. The detection and location data are then combined with any available ground truth information and compiled into a bulletin that will be released to the general public directly and eventually through the IRIS infrasound event bulletin. We use the open source Earthworm seismic data aggregation software to acquire waveform data either directly from the station operator or via the Incorporated Research Institutions for Seismology Data Management Center (IRIS DMC), if available. The data are processed using InfraMonitor, a powerful infrasound event detection and localization software program developed by Stephen Arrowsmith at Los Alamos National Laboratory (LANL). Our goal with this program is to provide the infrasound community with an event database that can be used collaboratively to study various natural and man-made sources. We encourage participation in this program directly or by making infrasound array data available through the IRIS DMC or other means. 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. R&A 5317326

  5. Analysis and modeling of infrasound from a four-stage rocket launch

    SciTech Connect

    Blom, Philip Stephen; Marcillo, Omar Eduardo; Arrowsmith, Stephen

    2016-06-17

    Infrasound from a four-stage sounding rocket was recorded by several arrays within 100 km of the launch pad. Propagation modeling methods have been applied to the known trajectory to predict infrasonic signals at the ground in order to identify what information might be obtained from such observations. There is good agreement between modeled and observed back azimuths, and predicted arrival times for motor ignition signals match those observed. The signal due to the high-altitude stage ignition is found to be low amplitude, despite predictions of weak attenuation. As a result, this lack of signal is possibly due to inefficient aeroacoustic coupling in the rarefied upper atmosphere.

  6. Analysis and modeling of infrasound from a four-stage rocket launch.

    PubMed

    Blom, Philip; Marcillo, Omar; Arrowsmith, Stephen

    2016-06-01

    Infrasound from a four-stage sounding rocket was recorded by several arrays within 100 km of the launch pad. Propagation modeling methods have been applied to the known trajectory to predict infrasonic signals at the ground in order to identify what information might be obtained from such observations. There is good agreement between modeled and observed back azimuths, and predicted arrival times for motor ignition signals match those observed. The signal due to the high-altitude stage ignition is found to be low amplitude, despite predictions of weak attenuation. This lack of signal is possibly due to inefficient aeroacoustic coupling in the rarefied upper atmosphere.

  7. IGRINS observations toward Class I disk sources

    NASA Astrophysics Data System (ADS)

    Lee, Seokho; Lee, Jeong-Eun; Park, Sunkyung; Jaffe, Daniel T.; Lee, Jae-Joon

    2015-08-01

    We present the high-resolution Immersion GRating INfrared spectrograph (IGRINS) spectra of Class I sources, including IRAS03445+3242 and IRAS04239+2436. These sources show the evidence of Keplerian disks; the broadened CO overtone (Δ v=2) transitions in emission and neutral metal lines (Mg I, Fe I, and Al I) in absorption. The thin Keplerian disk with a rotational velocity of ~100 km s-1 and a gas temperature of 5000 K at the innermost annulus can reproduce the CO overtone transitions including the bandhead emission. The temperature is assumed to have a power-law distribution with p=0.5. The outer colder disk or the envelope needs to fit the narrow absorption features overlaid on the broad emission lines in the CO overtone transitions. Other atomic and molecular emission lines likely radiated from the disk and/or wind are also detected.

  8. Sub-Surface Windscreen for the Measurement of Outdoor Infrasound

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Burkett, Cecil G., Jr.; Comeaux, Toby; Zuckerwar, Allan J.; Weistroffer, George R.

    2008-01-01

    A windscreen has been developed that features two advantages favorable for the measurement of outdoor infrasound. First, the sub-surface location, with the top of the windscreen flush with the ground surface, minimizes the mean velocity of the impinging wind. Secondly, the windscreen material (closed cell polyurethane foam) has a sufficiently low acoustic impedance (222 times that of air) and wall thickness (0.0127 m) to provide a transmission coefficient of nearly unity over the infrasonic frequency range (0-20 Hz). The windscreen, a tightly-sealed box having internal dimensions of 0.3048 x 0.3048 x 0.3556 m, contains a microphone, preamplifier, and a cable feed thru to an external power supply. Provisions are made for rain drainage and seismic isolation. A three-element array, configured as an equilateral triangle with 30.48 m spacing and operating continuously in the field, periodically receives highly coherent signals attributed to emissions from atmospheric turbulence. The time delays between infrasonic signals received at the microphones permit determination of the bearing and elevation of the sources, which correlate well with locations of pilot reports (PIREPS) within a 320 km radius about the array. The test results are interpreted to yield spectral information on infrasonic emissions from clear air turbulence.

  9. Electromagnetic geophysical observation with controlled source

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg

    2016-04-01

    In the paper the new theoretical and methodical approaches are examined for detailed investigations of the structure and state of the geological medium, and its behavior as a dynamic system in reaction to external man-made influences. To solve this problem it is necessary to use geophysical methods that have sufficient resolution and that are built on more complicated models than layered or layered-block models. One of these methods is the electromagnetic induction frequency-geometrical method with controlled sources. Here we consider new approaches using this method for monitoring rock shock media by means of natural experiments and interpretation of the practical results. That method can be used by oil production in mines, where the same events of non stability can occur. The key ideas of twenty first century geophysics from the point of view of geologist academician A.N. Dmitrievskiy [Dmitrievskiy, 2009] are as follows. "The geophysics of the twenty first century is an understanding that the Earth is a self-developing, self-supporting geo-cybernetic system, in which the role of the driving mechanism is played by the field gradients; the evolution of geological processes is a continuous chain of transformations and the interaction of geophysical fields in the litho- hydro- and atmosphere. The use of geophysical principles of a hierarchical quantum of geophysical space, non-linear effects, and the effects of reradiating geophysical fields will allow the creation of a new geophysics. The research, in which earlier only pure geophysical processes and technologies were considered, nowadays tends to include into consideration geophysical-chemical processes and technologies. This transformation will allow us to solve the problems of forecasting geo-objects and geo-processes in previously unavailable geological-technological conditions." The results obtained allow us to make the following conclusions, according to the key ideas of academician A.N. Dmitrievskiy: the rock

  10. Visualizing the deep end of sound: plotting multi-parameter results from infrasound data analysis

    NASA Astrophysics Data System (ADS)

    Perttu, A. B.; Taisne, B.

    2016-12-01

    Infrasound is sound below the threshold of human hearing: approximately 20 Hz. The field of infrasound research, like other waveform based fields relies on several standard processing methods and data visualizations, including waveform plots and spectrograms. The installation of the International Monitoring System (IMS) global network of infrasound arrays, contributed to the resurgence of infrasound research. Array processing is an important method used in infrasound research, however, this method produces data sets with a large number of parameters, and requires innovative plotting techniques. The goal in designing new figures is to be able to present easily comprehendible, and information-rich plots by careful selection of data density and plotting methods.

  11. Characterizing Explosive Eruptions at Sakurajima Volcano, Japan, Using Seismic, Infrasound, Lightning and Video Data

    NASA Astrophysics Data System (ADS)

    Smith, C. M.; Behnke, S. A.; Thomas, R. J.; Edens, H. E.; Cimarelli, C.; Cigala, V.; Van Eaton, A. R.; Iguchi, M.; Miki, D.; McNutt, S. R.

    2015-12-01

    The ability to determine volcanic ash plume characteristics from seismic and/or infrasonic records would enable increased accuracy in volcanic monitoring during times of low visibility. During May-June 2015 a field deployment of 6 infrasound sensors, 2 seismometers, multiple cameras, and 10 Lightning Mapping Array (LMA) stations were deployed around Sakurajima Volcano in Japan. During one month of observations (13 May to 10 June) hundreds of explosive eruptions were observed with plume heights reaching 4.3 km above the vent. The plumes varied in duration, ash content, and physical form. The resulting explosions exhibited a variety of infrasound waveforms including the classic long-period N shape as well as events with a mixture of high and low frequencies. For a subset of larger events, peak pressures ranged from 16 to 741 Pa at a distance of 3.6 km from the vent. The seismic signals are long period and emergent with no clear P or S-waves, although high frequency ground-coupled airwaves are visible in conjunction with the infrasonic record of some of the explosive eruptions. Peak ground displacements on the vertical component ranged from 2.1 to 183 um for the same subset of events. Volcanic lightning was both visually observed and recorded on the LMA stations. One of the goals of this project to determine if there are intrinsic relationships between ash plume characteristics, such as initial velocity or acceleration, ash grain size, texture, and composition, seismic and infrasound waveforms, and the presence and type of volcanic lightning. The rich variety of observations provides a good opportunity to determine such relationships.

  12. The role of infrasounds in maintaining whale herds

    NASA Astrophysics Data System (ADS)

    Payne, Roger S.

    2001-05-01

    For whales and dolphins a basic social unit is the herd. In several species, herds have been observed to maintain the same speed, direction, and membership overnight, and while swimming in waters of near-zero visibility-evidence that individuals can stay together using nonvisual cues. The most likely such cue is sound. If whale herds are held together with sound, yet we define herds as groups of whales seen moving together, then we are using visual criteria to judge what is an acoustic phenomenon, and our conclusions about a most basic unit of cetacean social structure, the herd, are at least incomplete, and, quite possibly, worthless. By calling herds, heards, we remind ourselves that sound controls herd size. We then consider that some whale infrasound can propagate across deep water at useful intensities (even in today's ship-noise-polluted ocean) for thousands of kilometers. The distance to which blue and fin whale sounds propagate before falling below background noise is given, and the possible advantages these whales obtain from such sounds is explored. The conclusion is that by sharing information on food finds infrasonically, fin and blue whales may have developed a way to divide up the food resources of an entire ocean.

  13. The correction of infrasound signals for upper atmospheric winds

    NASA Technical Reports Server (NTRS)

    Mutschlecner, J. Paul; Whitaker, Rodney W.

    1990-01-01

    Infrasound waves propagate in the atmosphere by a well known mechanism produced by refraction of the waves, return to earth, and reflection at the surface into the atmosphere for subsequent bounces. A figure illustrates this phenomenon with results from a ray trace model. In this instance three rays are returned to earth from a region centered at about 50 kilometers in altitude and two from a region near 110 kilometers in altitude. The control of the wave refraction is largely dominated by the temperature-height profile and inversions; however, a major influence is also produced by the atmospheric wind profile. Another figure illustrates the considerable ray differences for rays moving in the wind direction (to the right) and in the counter direction (to the left). It obviously can be expected that infrasonic signal amplitudes will be greatly influenced by the winds in the atmosphere. The seasonal variation of the high altitude atmospheric winds is well documented. A third figure illustrates this with average statistics on the observed zonal wind in the region of 50 plus or minus 5 kilometers in altitude. The results are based upon a survey by Webb; Webb terms this parameterization the Stratospheric Circulation Index (SCI). The very strong seasonal variation has the ability to exert a major seasonal influence on infrasonic signals. The purpose here is to obtain a method for the correction of this effect.

  14. The role of infrasounds in maintaining whale herds

    NASA Astrophysics Data System (ADS)

    Payne, Roger S.

    2004-05-01

    For whales and dolphins a basic social unit is the herd. In several species, herds have been observed to maintain the same speed, direction, and membership overnight, and while swimming in waters of near-zero visibility-evidence that individuals can stay together using nonvisual cues. The most likely such cue is sound. If whale herds are held together with sound, yet we define herds as groups of whales seen moving together, then we are using visual criteria to judge what is an acoustic phenomenon, and our conclusions about a most basic unit of cetacean social structure, the herd, are at least incomplete, and, quite possibly, worthless. By calling herds, heards, we remind ourselves that sound controls herd size. We then consider that some whale infrasound can propagate across deep water at useful intensities (even in today's ship-noise-polluted ocean) for thousands of kilometers. The distance to which blue and fin whale sounds propagate before falling below background noise is given, and the possible advantages these whales obtain from such sounds is explored. The conclusion is that by sharing information on food finds infrasonically, fin and blue whales may have developed a way to divide up the food resources of an entire ocean.

  15. Evaluation of Inter-Mountain Labs infrasound sensors : July 2007.

    SciTech Connect

    Hart, Darren M.

    2007-10-01

    Sandia National Laboratories has tested and evaluated three Inter Mountain Labs infrasound sensors. The test results included in this report were in response to static and tonal-dynamic input signals. Most test methodologies used were based on IEEE Standards 1057 for Digitizing Waveform Recorders and 1241 for Analog to Digital Converters; others were designed by Sandia specifically for infrasound application evaluation and for supplementary criteria not addressed in the IEEE standards. The objective of this work was to evaluate the overall technical performance of the Inter Mountain Labs (IML) infrasound sensor model SS. The results of this evaluation were only compared to relevant noise models; due to a lack of manufactures documentation notes on the sensors under test prior to testing. The tests selected for this system were chosen to demonstrate different performance aspects of the components under test.

  16. Steps toward quantitative infrasound propagation modeling

    NASA Astrophysics Data System (ADS)

    Waxler, Roger; Assink, Jelle; Lalande, Jean-Marie; Velea, Doru

    2016-04-01

    Realistic propagation modeling requires propagation models capable of incorporating the relevant physical phenomena as well as sufficiently accurate atmospheric specifications. The wind speed and temperature gradients in the atmosphere provide multiple ducts in which low frequency sound, infrasound, can propagate efficiently. The winds in the atmosphere are quite variable, both temporally and spatially, causing the sound ducts to fluctuate. For ground to ground propagation the ducts can be borderline in that small perturbations can create or destroy a duct. In such cases the signal propagation is very sensitive to fluctuations in the wind, often producing highly dispersed signals. The accuracy of atmospheric specifications is constantly improving as sounding technology develops. There is, however, a disconnect between sound propagation and atmospheric specification in that atmospheric specifications are necessarily statistical in nature while sound propagates through a particular atmospheric state. In addition infrasonic signals can travel to great altitudes, on the order of 120 km, before refracting back to earth. At such altitudes the atmosphere becomes quite rare causing sound propagation to become highly non-linear and attenuating. Approaches to these problems will be presented.

  17. Seismo-acoustic Signals Recorded at KSIAR, the Infrasound Array Installed at PS31

    NASA Astrophysics Data System (ADS)

    Kim, T. S.; Che, I. Y.; Jeon, J. S.; Chi, H. C.; Kang, I. B.

    2014-12-01

    One of International Monitoring System (IMS)'s primary seismic stations, PS31, called Korea Seismic Research Station (KSRS), was installed around Wonju, Korea in 1970s. It has been operated by US Air Force Technical Applications Center (AFTAC) for more than 40 years. KSRS is composed of 26 seismic sensors including 19 short period, 6 long period and 1 broad band seismometers. The 19 short period sensors were used to build an array with a 10-km aperture while the 6 long period sensors were used for a relatively long period array with a 40-km aperture. After KSRS was certified as an IMS station in 2006 by Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), Korea Institute of Geoscience and Mineral Resources (KIGAM) which is the Korea National Data Center started to take over responsibilities on the operation and maintenance of KSRS from AFTAC. In April of 2014, KIGAM installed an infrasound array, KSIAR, on the existing four short period seismic stations of KSRS, the sites KS05, KS06, KS07 and KS16. The collocated KSIAR changed KSRS from a seismic array into a seismo-acoustic array. The aperture of KSIAR is 3.3 km. KSIAR also has a 100-m small aperture infrasound array at KS07. The infrasound data from KSIAR except that from the site KS06 is being transmitted in real time to KIGAM with VPN and internet line. An initial analysis on seismo-acoustic signals originated from local and regional distance ranges has been performed since May 2014. The analysis with the utilization of an array process called Progressive Multi-Channel Correlation (PMCC) detected seismo-acoustic signals caused by various sources including small explosions in relation to constructing local tunnels and roads. Some of them were not found in the list of automatic bulletin of KIGAM. The seismo-acoustic signals recorded by KSIAR are supplying a useful information for discriminating local and regional man-made events from natural events.

  18. Tracking near-surface atmospheric conditions using an infrasound network.

    PubMed

    Marcillo, O; Johnson, J B

    2010-07-01

    Continuous volcanic infrasound signal was recorded on a three-microphone network at Kilauea in July 2008 and inverted for near-surface horizontal winds. Inter-station phase delays, determined by signal cross-correlation, vary by up to 4% and are attributable to variable atmospheric conditions. The results suggest two predominant weather regimes during the study period: (1) 6-9 m/s easterly trade winds and (2) lower-intensity 2-5 m/s mountain breezes from Mauna Loa. The results demonstrate the potential of using infrasound for tracking local averaged meteorological conditions, which has implications for modeling plume dispersal and quantifying gas flux.

  19. 2013 Russian Fireball Largest Ever Detected by CTBTO Infrasound Sensors (Invited)

    NASA Astrophysics Data System (ADS)

    Pilger, C.; Ceranna, L.; Le Pichon, A.; Herry, P.; Brachet, N.; Mialle, P.; Brown, D.

    2013-12-01

    On 15 February 2013 at 03h20 UT, a large Earth impacting fireball disintegrated over the Ural Mountains near the city of Chelyabinsk. The bolide produced shock waves that blew out windows, injured hundreds of people and damaged buildings in many surrounding cities. Infrasonic waves generated by the explosion propagated over very long distances. The event was globally detected by 20 arrays part of the 44 operating infrasound IMS (International Monitoring System) stations of the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization). This fireball event provides a prominent milestone for studying, in detail, infrasound propagation traveling twice around the globe for almost two days at distances larger than 80000 km. Therefore, its analysis offers a unique opportunity to calibrate detection and location methods and evaluate the global performance of the IMS network. The presentation will provide an overview on the global recordings and analyses. Moreover, in order to explain the detection capability of the overall operating IMS network, range-dependent propagation modeling considering both a point-like explosive source and a line source is performed.

  20. The multidisciplinary, Seismic-Hydroacoustic-Infrasound, observatory in offshore site of the northeastern South Korea

    NASA Astrophysics Data System (ADS)

    Cho, H. M.; Che, I. Y.; Kim, G.; Lim, I. S.; Shin, I. C.; Kim, Y.

    2016-12-01

    The long-term seismic observation on the sea-floor is a challenging idea that can provide useful information in offshore area and help us to understand the tectonics better. Projects in the United States, Canada, Japan, and Europe were successfully implemented. We report on the installation of a long-term sea-floor multidisciplinary observatory in offshore site of the northeastern South Korea. The site is located 4.5 km from the shore, at a water depth of about 80 m. The novelty of our project is the development of an integrated detection system for earthquake combining seismic, hydroacoutic, and infrasound technologies. The observatory consists of three sea-floor seismometer modules and associated elastic beacon type buoys each of which is equipped with solar power supply, infrasound and meteorological sensors, RF and LTE network for continuous and real-time data transmission, and SOH system. Three elastic beacon type buoys were successfully deployed during July 29 - 31, 2015. The sea-floor seismometer module is equipped with a 3-component CMG-3T-OBS system with 24-bit 8-channel digitizer in titanium sphere. A current meter, a Differential Pressure Gauge, and a HTI hydrophone are mounted on the lifting frame. The whole module is covered and protected with Trawl resistant concrete dome. Three land broadband seismic stations nearby (< 40 km) can provide the comparison of background noise between land and ocean. We analyzed the seismic ambient noise characteristics on the offshore site from the data of temporary OBS operated for 4 months. The power spectral density was calculated and compared with the NLNM and NHNM. Now, we are preparing the installation of three seismometer modules scheduled to do in early September, 2016. The integrated data and the technique analyzing the Seismic-Hydroacoustic-Infrasound data will improve our detection system for earthquake in offshore.

  1. Determination of uncertainty in the estimation of velocity and direction-of-arrival for atmospheric infrasound signals

    NASA Astrophysics Data System (ADS)

    Szuberla, Curt A. L.; Olson, John V.

    2002-11-01

    Upon the detection of an atmospheric infrasound signal, the problem of precisely estimating the signal's velocity (v) and direction-of-arrival (theta) arises. Multiple sources, multipath, medium anisotropies, and other propagation effects can all degrade precision; however, uncertainty in the estimates of v and theta is fundamentally governed by array geometry and the estimation of time delays across the array. Typically, as in the Comprehensive Test Ban Treaty Organzation Provisional Technical Secretariat (CTBTO/PTS) specification for data from infrasound stations, the Cramer-Rao lower bound is invoked to ascertain the uncertainties associated with v and theta. As this theoretical lower limit is often overly conservative, a more general, and useful, approach to calculate these uncertainties is developed. Examples of this uncertainty determination are presented for typical impulsive and continuous atmospheric infrasound signals received at arrays in Windless Bight, Antarctica and Fairbanks, Alaska. Since the determination of v and theta serves as primary input to any propogation model, it is critical that uncertainties in these estimates be addressed. As an extension of this work, an interactive graphical tool is constructed to assist in the analysis of performance bounds for arbitrary array geometries and signal characteristics.

  2. Investigating the tremor source process at Fuego volcano, Guatemala through bench-scale analogue modeling

    NASA Astrophysics Data System (ADS)

    Lyons, J. J.; Ichihara, M.; Lees, J. M.; Waite, G. P.

    2011-12-01

    the seismic and infrasound tremor by constructing an analogue model that can reproduce some of the same tremor characteristics observed in the natural samples. The model consists of a simple conduit connected to a tank containing a viscoelastic fluid. A flapping membrane is placed in the conduit and is oscillated by the flow of compressed gas. The signal is then pumped through the viscoelastic fluid. Broadband pressure transducers record pressure changes in the conduit up-and downstream of the signal generator, and three broadband microphones positioned around the tank record the signal transmitted in the atmosphere. In addition, high-speed and standard video cameras record the experiment, in particular the details of the injection of the gas into the fluid. By varying the gas pressure, we produce bubble bursting or harmonic tremor, and by controlling the elasticity in the conduit and depth of the fluid we reproduce some of the signal characteristics observed in the Fuego tremor, thus providing further constraint on the source mechanics of seismic and infrasound tremor.

  3. Observation of soft X-rays from cosmic sources

    NASA Technical Reports Server (NTRS)

    Catura, R. C.; Acton, L. W.

    1975-01-01

    A binary X-ray source, an extended extragalactic X-ray source and several nearby stars were surveyed for X-ray emission. The energy spectrum and time structure of X-ray flux from the binary source, Her X-l, was investigated in the range from 0.15 to 6 KeV. This source was observed at a binary phase of 0.18 with the system near elongation normal to the line of sight. Intense pulsations were observed in optical emission lines near this binary phase. The spectrum and angular distribution of X-ray emission from the X-ray source in the Virgo Cluster of Galaxies, near M 87, was also observed. In addition, the stars Alpha Leo, Zeta Her, and Epsilon Vir were investigated. Epsilon Aur and Alpha Aur were also scanned. These stars were studied since there is increasing evidence that such objects may be transient sources of soft X-rays.

  4. XMM-Newton and Chandra observations of SHEEP sources

    NASA Astrophysics Data System (ADS)

    Georgantopoulos, I.; Nandra, K.; Brotherton, M.; Georgakakis, A.; Papadakis, I. E.; O'Neill, P.

    2006-04-01

    We present Chandra and XMM-Newton observations of 12 bright [f(2-10keV) > 10-13ergcm-2s-1] sources from the ASCA search for the High Energy Extragalactic Population (SHEEP) survey. Most of these have been either not observed or not detected previously with the ROSAT mission, and therefore they constitute a sample biased towards hard sources. The Chandra observations are important in locating the optical counterpart of the X-ray sources with accuracy. Optical spectroscopic observations show that our sample is associated with both narrow-line (NL) (six objects) and broad-line (BL) active galactic nuclei (AGN) (five objects), with one source remaining unidentified. Our sources cover the redshift range 0.04-1.29, spanning luminosities from 1042 to 1045ergs-1 (2-10 keV). The NL sources have preferentially lower redshift (and luminosity) compared to the BL ones. This can be most easily explained in a model where the NL AGN are intrinsically less luminous than the BL ones in line with the results of Steffen et al. The X-ray spectral fittings show a roughly equal number of obscured (NH > 1022cm-2) and unobscured (NH < 1022cm-2) sources. There is a clear tendency for obscured sources to be associated with NL AGN and unobscured sources with BL ones. However, there is a marked exception with the highest obscuring column observed at a BL AGN at a redshift of z= 0.5.

  5. Using Infrasound and Machine Learning for Monitoring Plinian Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Ham, F. M.; Iyengar, I.; Hambebo, B. M.; Garces, M. A.; Deaton, J.; Perttu, A.; Williams, B.

    2012-12-01

    Large plinian volcanic eruptions can inject a substantial amount of volcanic gas and ash into the stratosphere. This can present a severe hazard to commercial air traffic. A hazardous Icelandic volcanic ash-eruption was reported on April 14, 2010. This resulted in London's aviation authority to issue an alert that an ash plume was moving from an eruption in Iceland towards northwestern Europe. This eruption resulted in the closure of large areas of European airspace. Large plinian volcanic eruptions radiate infrasonic signals that can be detected by a global infrasound array network. To reduce potential hazards for commercial aviation from volcanic ash, these infrasound sensor arrays have been used to detect infrasonic signals released by sustained volcanic eruptions that can inject ash into the stratosphere at aircraft's cruising altitudes, typically in the order of 10km. A system that is capable of near, real-time eruption detection and discrimination of plinian eruptions from other natural phenomena that can produce infrasound with overlapping spectral content (0.01 to 0.1 Hz) is highly desirable to provide ash-monitoring for commercial aviation. In the initial study, cepstral features were extracted from plinian volcanic eruptions and mountain associated wave infrasound signals. These feature vectors were then used to train and test a two-module neural network classifier (radial basis function neural networks were used for each module). One module is dedicated to classifying plinian volcanic eruptions, the other mountain associated waves. Using an independent validation dataset, the classifier's correct classification rate was 91.5%. Then a different two-module neural network classifier was designed to discriminate between plinian volcanic eruptions and a collection of infrasound signals that are not-of-interest but have spectral content that overlaps with the volcano signals. One module is again dedicated to classifying plinian volcanic eruptions, however, in

  6. IVS Observation of ICRF2-Gaia Transfer Sources

    NASA Astrophysics Data System (ADS)

    Le Bail, K.; Gipson, J. M.; Gordon, D.; MacMillan, D. S.; Behrend, D.; Thomas, C. C.; Bolotin, S.; Himwich, W. E.; Baver, K. D.; Corey, B. E.; Titus, M.; Bourda, G.; Charlot, P.; Collioud, A.

    2016-03-01

    The second realization of the International Celestial Reference Frame (ICRF2), which is the current fundamental celestial reference frame adopted by the International Astronomical Union, is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency’s Gaia mission, launched on 2013 December 19, started routine scientific operations in 2014 July. By scanning the whole sky, it is expected to observe ∼500,000 Quasi Stellar Objects in the optical domain an average of 70 times each during the five years of the mission. This means that, in the future, two extragalactic celestial reference frames, at two different frequency domains, will coexist. It will thus be important to align them very accurately. In 2012, the Laboratoire d’Astrophysique de Bordeaux (LAB) selected 195 sources from ICRF2 that will be observed by Gaia and should be suitable for aligning the radio and optical frames: they are called ICRF2-Gaia transfer sources. The LAB submitted a proposal to the International VLBI Service (IVS) to regularly observe these ICRF2-Gaia transfer sources at the same rate as Gaia observes them in the optical realm, e.g., roughly once a month. We describe our successful effort to implement such a program and report on the results. Most observations of the ICRF2-Gaia transfer sources now occur automatically as part of the IVS source monitoring program, while a subset of 37 sources requires special attention. Beginning in 2013, we scheduled 25 VLBI sessions devoted in whole or in part to measuring these 37 sources. Of the 195 sources, all but one have been successfully observed in the 12 months prior to 2015 September 01. Of the sources, 87 met their observing target of 12 successful sessions per year. The position uncertainties of all of the ICRF2-Gaia transfer sources have improved since the start of this observing program. For a subset of 24 sources whose positions were very poorly known, the uncertainty

  7. A dedicated pistonphone for absolute calibration of infrasound sensors at very low frequencies

    NASA Astrophysics Data System (ADS)

    He, Wen; He, Longbiao; Zhang, Fan; Rong, Zuochao; Jia, Shushi

    2016-02-01

    Aimed at the absolute calibration of infrasound sensors at very low frequencies, an upgraded and improved infrasonic pistonphone has been developed. The pistonphone was designed such that a very narrow clearance between the piston and its guide was realized based on an automatically-centered clearance-sealing structure, and a large volume rigid-walled chamber was also adopted, which improved the leakage time-constant of the chamber. A composite feedback control system was applied to the electromagnetic vibrator to control the precise motion of the piston. Performance tests and uncertainty analysis show that the leakage time-constant is so large, and the distortion of the sound pressure is so small, that the pistonphone can be used as a standard infrasound source in the frequency range from 0.001 Hz to 20 Hz. The low frequency property of the pistonphone has been verified through calibrating low frequency microphones. Comparison tests with the reciprocity method have shown that the pressure sensitivities from the pistonphone are not only reliable at common frequencies but also have smaller uncertainties at low frequencies.

  8. The use of an infrasound microphone array to study wind noise spectra and correlation

    NASA Astrophysics Data System (ADS)

    Shields, F. Douglas; Talmadge, Carrick

    2003-04-01

    A three dimensional array of infrasound sensors of original design has been constructed and used to study wind generated pressure signals in the frequency range from 0.1 to 100 Hz. The ten sensors in each arm of the array are 2 feet apart. An ultrasonic anemometer ten feet off the ground was used to make simultaneous measurements of the three components of the wind velocity. Several sets of data have been taken in open fields with different ground cover. The data have been spectrally analyzed and, over a limited frequency range, the velocity and pressure variations found to obey the 5/3 and 7/3 power law that is expected for the inertial range. A study has also been made of the dependence of the correlation between the pressure signals and the sensor separation. The coherence of the pressure signals indicates that the convection velocity is nearly independent of frequency, and the correlation has an exponentially decaying sinusoidal dependence on the sensor separation. The array has also been used successfully to localize infrasound sources. [Work supported by the U.S. Army Armament Research Development and Engineering Center.

  9. On infrasound detector performances using data set with modeled coherence loss

    NASA Astrophysics Data System (ADS)

    Nouvellet, A.; Charbit, M. J.; Le Pichon, A.

    2013-12-01

    An important issue of any infrasound monitoring array is the detection of coherent infrasound signals buried in a background noise and then estimate their features, more specifically the direction of arrival (DOA) and the velocity. Many recent studies have been devoted to the detection problem (e.g. Y. Cansi 1995, R. H. Shumway 2001, S. J. Arrowsmith 2008, D. J. Brown 2008, W. B. Howard 2010, K. Walker 2010). The Fisher function of test (FoT) is a commonly used detector of signal of interest (SOI) in additive white gaussian noise. This FoT is derived assuming that the signals are delayed considering a planar wavefront propagation. Such hypothesis induces a magnitude square coherence (MSC) equal to 1 for all frequencies. This assumption fails in practice as first shown by H. Mack and E. A. Flinn (1971). The basic idea is to derive the loss of coherence from uncertainties on the source wavefront. This wavefront uncertainty is modeled as a random vector which is the sum of a deterministic wavenumber, and a gaussian zero-mean random vector characterized by its covariance matrix. In this study we first present the procedure to generate synthetic signals with controlled loss of coherence and then we derive the estimated ROC curves of the Fisher detector. Numerical results show the degradation of the detector performances when considering the loss of coherence, more specifically for large aperture array and high frequency SOI.

  10. Detailed observations of the source of terrestrial narrowband electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.

    1982-01-01

    Detailed observations are presented of a region near the terrestrial plasmapause where narrowband electromagnetic radiation (previously called escaping nonthermal continuum radiation) is being generated. These observations show a direct correspondence between the narrowband radio emissions and electron cyclotron harmonic waves near the upper hybrid resonance frequency. In addition, electromagnetic radiation propagating in the Z-mode is observed in the source region which provides an extremely accurate determination of the electron plasma frequency and, hence, density profile of the source region. The data strongly suggest that electrostatic waves and not Cerenkov radiation are the source of the banded radio emissions and define the coupling which must be described by any viable theory.

  11. Kernel-based machine learning techniques for infrasound signal classification

    NASA Astrophysics Data System (ADS)

    Tuma, Matthias; Igel, Christian; Mialle, Pierrick

    2014-05-01

    Infrasound monitoring is one of four remote sensing technologies continuously employed by the CTBTO Preparatory Commission. The CTBTO's infrasound network is designed to monitor the Earth for potential evidence of atmospheric or shallow underground nuclear explosions. Upon completion, it will comprise 60 infrasound array stations distributed around the globe, of which 47 were certified in January 2014. Three stages can be identified in CTBTO infrasound data processing: automated processing at the level of single array stations, automated processing at the level of the overall global network, and interactive review by human analysts. At station level, the cross correlation-based PMCC algorithm is used for initial detection of coherent wavefronts. It produces estimates for trace velocity and azimuth of incoming wavefronts, as well as other descriptive features characterizing a signal. Detected arrivals are then categorized into potentially treaty-relevant versus noise-type signals by a rule-based expert system. This corresponds to a binary classification task at the level of station processing. In addition, incoming signals may be grouped according to their travel path in the atmosphere. The present work investigates automatic classification of infrasound arrivals by kernel-based pattern recognition methods. It aims to explore the potential of state-of-the-art machine learning methods vis-a-vis the current rule-based and task-tailored expert system. To this purpose, we first address the compilation of a representative, labeled reference benchmark dataset as a prerequisite for both classifier training and evaluation. Data representation is based on features extracted by the CTBTO's PMCC algorithm. As classifiers, we employ support vector machines (SVMs) in a supervised learning setting. Different SVM kernel functions are used and adapted through different hyperparameter optimization routines. The resulting performance is compared to several baseline classifiers. All

  12. Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

    NASA Astrophysics Data System (ADS)

    Assink, J. D.; Pichon, A. Le; Blanc, E.; Kallel, M.; Khemiri, L.

    2014-07-01

    In this paper, we evaluate vertical wind and temperature profiles that are produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric analysis. The evaluation is carried out on both hemispheres: we make use of stratospheric infrasound arrivals from Mount Etna (37°N) and Mount Yasur (22°S). The near-continuous, high activity of both volcanoes permits the study of stratospheric propagation along well-defined paths with a time resolution ranging from hours to multiple years. Infrasound observables are compared to theoretical estimates obtained from acoustic propagation modeling using the ECMWF analysis. While a first-order agreement is found for both hemispheres, we report on significant discrepancies around some of the equinox periods and other intervals during which the atmosphere is in a state of transition and dynamical oscillations of the atmosphere dominate over the general circulation. We present an inversion study in which we make use of measured trace velocity estimates to estimate first-order effective sound speed model updates in a Bayesian framework. Deviations from the a priori models around the stratopause up to 10% (≈ 30 m s-1) are estimated. Such updates are in line with the results from comparisons between ECMWF analysis and observations from lidar and microwave Doppler spectroradiometer facilities that were colocated during the course of the 2012-2013 Atmospheric dynamics Research and InfraStructure in Europe (ARISE) measurement campaign.

  13. How to Identify an Infection Source With Limited Observations

    NASA Astrophysics Data System (ADS)

    Luo, Wuqiong; Tay, Wee Peng; Leng, Mei

    2014-08-01

    A rumor spreading in a social network or a disease propagating in a community can be modeled as an infection spreading in a network. Finding the infection source is a challenging problem, which is made more difficult in many applications where we have access only to a limited set of observations. We consider the problem of estimating an infection source for a Susceptible-Infected model, in which not all infected nodes can be observed. When the network is a tree, we show that an estimator for the source node associated with the most likely infection path that yields the limited observations is given by a Jordan center, i.e., a node with minimum distance to the set of observed infected nodes. We also propose approximate source estimators for general networks. Simulation results on various synthetic networks and real world networks suggest that our estimators perform better than distance, closeness, and betweenness centrality based heuristics.

  14. Identification of blasting sources in the Dobrogea seismogenic region, Romania using seismo-acoustic signals

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela Veronica; Grecu, Bogdan; Popa, Mihaela; Radulian, Mircea

    2016-10-01

    In order to discriminate between quarry blasts and earthquakes observed in the Dobrogea seismogenic region, a seismo-acoustic analysis was performed on 520 events listed in the updated Romanian seismic catalogue from January 2011 to December 2012. During this time interval, 104 seismo-acoustic events observed from a distance between 110 and 230 km and backazimuth interval of 110-160° from the IPLOR infrasound array were identified as explosions by associating with infrasonic signals. WinPMCC software for interactive analysis was applied to detect and characterize infrasonic signals in terms of backazimuth, speed and frequency content. The measured and expected values of both backazimuths and arrival times for the study events were compared in order to identify the sources of infrasound. Two predominant directions for seismo-acoustic sources' aligning were observed, corresponding to the northern and central parts of Dobrogea, and these directions are further considered as references in the process of discriminating explosions from earthquakes. A predominance of high-frequency detections (above 1 Hz) is also observed in the infrasound data. The strong influence of seasonally dependent stratospheric winds on the IPLOR detection capability limits the efficiency of the discrimination procedure, as proposed by this study.

  15. The first second of volcanic eruptions from the Erebus volcano lava lake, Antarctica—Energies, pressures, seismology, and infrasound

    NASA Astrophysics Data System (ADS)

    Gerst, A.; Hort, M.; Aster, R. C.; Johnson, J. B.; Kyle, P. R.

    2013-07-01

    We describe a multiparameter experiment at Erebus volcano, Antarctica, employing Doppler radar, video, acoustic, and seismic observations to estimate the detailed energy budget of large (up to 40 m-diameter) bubble bursts from a persistent phonolite lava lake. These explosions are readily studied from the crater rim at ranges of less than 500 m and present an ideal opportunity to constrain the dynamics and mechanism of magmatic bubble bursts that can drive Strombolian and Hawaiian eruptions. We estimate the energy budget of the first second of a typical Erebus explosion as a function of time and energy type. We constrain gas pressures and forces using an analytic model for the expansion of a gas bubble above a conduit that incorporates conduit geometry and magma and gas parameters. The model, consistent with video and radar observations, invokes a spherical bulging surface with a base diameter equal to that of the lava lake. The model has no ad hoc free parameters, and geometrical calculations predict zenith height, velocity, and acceleration during shell expansion. During explosions, the energy contained in hot overpressured gas bubbles is freed and partitioned into other energy types, where by far the greatest nonthermal energy component is the kinetic and gravitational potential energy of the accelerated magma shell (>109 J). Seismic source energy created by explosions is estimated from radar measurements and is consistent with source energy determined from seismic observations. For the generation of the infrasonic signal, a dual mechanism incorporating a terminally disrupted slug is proposed, which clarifies previous models and provides good fits to observed infrasonic pressures. A new and straightforward method is presented for determining gas volumes from slug explosions at volcanoes from remote infrasound recordings.

  16. Infrasound as a Geophysical Probe Using Earth as a Venus Analog

    NASA Astrophysics Data System (ADS)

    Komjathy, A.; Cutts, J. A.; Pauken, M.; Kedar, S.; Smrekar, S. E.; Hall, J. R.

    2016-12-01

    JPL is in a process of developing an instrument to measure seismic activity on Venus by detecting infrasonic waves in the atmosphere. The overall objective of this research is to demonstrate the feasibility of using sensitive barometers to detect infrasonic signals from seismic and explosive activity on Venus from a balloon platform. Because of Venus' dense atmosphere, seismic signatures from even small quakes (magnitude 3) are effectively coupled into the atmosphere. The seismic signals are known to couple about 60 times more efficiently into the atmosphere on Venus than on Earth. It was found that almost no attenuation below 80 km on Venus for frequency less than 1Hz. Whereas wind noise is a major source of background noise for terrestrial infrasonic arrays, it is expected that a balloon platform, which drifts with winds will be capable of very sensitive measurements with low noise. In our research we will demonstrate and apply techniques for discriminating upward propagating waves from a seismic event by making measurements with two or more infrasonic sensors using very sensitive barometers on a tether deployed from the balloon in a series of earth-based tests. We will first demonstrate and validate the technique using an artificial infrasound source in a deployment from a hot air balloon on Earth and then extend it with longer duration flights in the troposphere and stratosphere. We will report results on the first flight experiment that will focus on using the barometer instruments on a tethered helium-filled balloon. The balloon flight will be conducted in the vicinity of a known seismic source generated by a seismic hammer. Earlier tests conducted by Sandia National Laboratory demonstrated that this is a highly reproducible source of seismic and acoustic energy using infrasound sensors. The results of the experiments are intended to validate the two-barometer signal processing approach using a well-characterized point signal source.

  17. Infrasound as a Geophysical Probe Using Earth as a Venus Analog

    NASA Astrophysics Data System (ADS)

    Komjathy, Attila; Cutts, James; Pauken, Michael; Kedar, Sharon; Smrekar, Suzanne

    2016-10-01

    JPL is in a process of developing an instrument to measure seismic activity on Venus by detecting infrasonic waves in the atmosphere. The overall objective of this research is to demonstrate the feasibility of using sensitive barometers to detect infrasonic signals from seismic and explosive activity on Venus from a balloon platform. Because of Venus' dense atmosphere, seismic signatures from even small quakes (magnitude ~3) are effectively coupled into the atmosphere. The seismic signals are known to couple about 60 times more efficiently into the atmosphere on Venus than on Earth. It was found that almost no attenuation below 80 km on Venus for frequency less than 1Hz. Whereas wind noise is a major source of background noise for terrestrial infrasonic arrays, it is expected that a balloon platform, which drifts with winds will be capable of very sensitive measurements with low noise.In our research we will demonstrate and apply techniques for discriminating upward propagating waves from a seismic event by making measurements with two or more infrasonic sensors using very sensitive barometers on a tether deployed from the balloon in a series of earth-based tests. We will first demonstrate and validate the technique using an artificial infrasound source in a deployment from a hot air balloon on Earth and then extend it with longer duration flights in the troposphere and stratosphere.We will report results on the first flight experiment that will focus on using the barometer instruments on a tethered helium-filled balloon. The balloon flight will be conducted in the vicinity of a known seismic source generated by a seismic hammer. Earlier tests conducted by Sandia National Laboratory demonstrated that this is a highly reproducible source of seismic and acoustic energy using infrasound sensors. The results of the experiments are intended to validate the two-barometer signal processing approach using a well-characterized point signal source.

  18. ANTARES explosion as recorded by the US-ARRAY: an unprecedented ground-truth infrasound event

    NASA Astrophysics Data System (ADS)

    Vergoz, Julien; Millet, Christophe; Le Pichon, Alexis

    2016-04-01

    The 28th October 2014 in Wallops Flight Facility, orbital's Antares launch vehicle failed and heavily exploded onto the launch pad area. At that time, the US transportable array of more than 200 operating stations (all equipped with microbarometers), was located on the east coast of the US and surrounded the accident. A large amount and variety of infrasound phases were observed at some stations, highlighting interesting propagation effects. The variety of recorded signals on such a dense network is unprecedented and offers the opportunity to better understand some propagation features, such as (1) the frequency content changes of stratospheric phases; (2) the dispersion of tropospheric phases propagating over thousands of kilometers within a stable and thin waveguide at fast phase speeds (350m/s) with low attenuation; (3) the non-linear effects associated with slow thermospheric phases (180m/s), especially in terms of shape, amplitude and duration. These 3 points will be addressed, and pieces of interpretations will be given thanks to the different propagation techniques: full waveform modelling (Normal Modes, finite element method), parabolic equation and ray tracing technique. Location issues of such an acoustic event based on tens of infrasound arrival times only will also be shown and discussed.

  19. Observations of galactic X-ray sources by OSO-7

    NASA Technical Reports Server (NTRS)

    Markert, T. H.; Canizares, C. R.; Clark, G. W.; Hearn, D. R.; Li, F. K.; Sprott, G. F.; Winkler, P. F.

    1977-01-01

    We present the MIT data from the OSO-7 satellite for observations of the galactic plane between 1971 and 1974. A number of sources discovered in the MIT all-sky survey are described in detail: MX 0049 + 59, MX 0836 - 42, MX 1353 - 64, MX 1406 - 61, MX 1418 - 61, MX 1709 - 40, and MX 1608 - 52 (the persistent source suggested to be associated with the X-ray burst source XB 1608 - 52). Upper limits to the X-ray emission from a number of interesting objects are also derived. General results describing all of our observations of galactic sources are presented. Specifically, we display the number-intensity diagrams, luminosity functions, and color-color diagrams for all of the sources we detected. The data are divided between disk and bulge populations, and the characteristics of the two groups are contrasted. Finally, the concept of X-ray source populations and the relationship of globular cluster sources and burst sources to the disk and bulge populations are discussed.

  20. Siberian Arctic black carbon sources constrained by model and observation.

    PubMed

    Winiger, Patrik; Andersson, August; Eckhardt, Sabine; Stohl, Andreas; Semiletov, Igor P; Dudarev, Oleg V; Charkin, Alexander; Shakhova, Natalia; Klimont, Zbigniew; Heyes, Chris; Gustafsson, Örjan

    2017-02-14

    Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ng⋅m(-3) to 302 ng⋅m(-3)) and dual-isotope-constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth.

  1. Siberian Arctic black carbon sources constrained by model and observation

    PubMed Central

    Andersson, August; Eckhardt, Sabine; Stohl, Andreas; Semiletov, Igor P.; Dudarev, Oleg V.; Charkin, Alexander; Shakhova, Natalia; Klimont, Zbigniew; Heyes, Chris; Gustafsson, Örjan

    2017-01-01

    Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ng⋅m−3 to 302 ng⋅m−3) and dual-isotope–constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth. PMID:28137854

  2. Siberian Arctic black carbon sources constrained by model and observation

    NASA Astrophysics Data System (ADS)

    Winiger, Patrik; Andersson, August; Eckhardt, Sabine; Stohl, Andreas; Semiletov, Igor P.; Dudarev, Oleg V.; Charkin, Alexander; Shakhova, Natalia; Klimont, Zbigniew; Heyes, Chris; Gustafsson, Örjan

    2017-02-01

    Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ngṡm-3 to 302 ngṡm-3) and dual-isotope-constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth.

  3. Looking for a correlation between infrasound and volcanic gas in strombolian explosions by using high resolution UV spectroscopy and thermal imagery

    NASA Astrophysics Data System (ADS)

    Delle Donne, Dario; Tamburello, Giancarlo; Ripepe, Maurizio; Aiuppa, Alessandro

    2014-05-01

    According to the linear theory of sound, acoustic pressure propagating in a homogeneous atmosphere can be modelled in terms of the rate of change of a volumetric source. At open-vent volcanoes, this acoustic source process is commonly related to the explosive dynamics triggered by the rise, expansion and bursting of a gas slug at the magma free surface with the conduit. Just before an explosion, the magma surface will undergo deformation by the expanding gas slug. The deformation of the magma surface will then produce an equivalent displacement of the atmosphere, inducing a volumetric compression and generating an excess pressure that scales to the rate of volumetric change of the atmosphere displaced. Linear theory of sound thus predicts that pressure amplitude of infrasonic waves associated to volcanic explosions should be generated by the first time-derivative of the gas mass flux during the burst. In some cases a correlation between the first time-derivative and the SO2 mass flux has been found. However no clear correlation has yet been established between infrasonic amplitude and total ejected gas mass; therefore, the origin of infrasound in volcanic systems remains matter of debate. In the framework of the FP7-ERC BRIDGE Project, we tested different possible hypotheses on the acoustic source model, by correlating infrasound with the total gas mass retrieved from high-resolution UV spectroscopy techniques (UV camera). Experiments were conducted at Stromboli volcano (Italy), where we also employed a thermal camera to measure the total fragments/gas mass. Both techniques allowed independent estimation of total mass flux of gas and fragments within the volcanic plume. During the experiments, explosions detected by the UV camera emitted between 2 and 55 kg SO2, corresponding to SO2 peak fluxes of 0.1-0.8 kg/s. SO2 mass was converted into a total (maximum) erupted gas of 1310 kg, which is generating a peak pressure of ~8 Pa recorded at ~450 m from the source vent

  4. Viking observations at the source region of auroral kilometric radiation

    SciTech Connect

    Bahnsen, A.; Jespersen, M.; Ungstrup, E. ); Pedersen, B.M. ); Eliasson, L. ); Murphree, J.S.; Elphinstone, R.D. ); Blomberg, L. ); Holmgren, G. ); Zanetti, L.J. )

    1989-06-01

    The orbit of the Swedish satellite Viking was optimized for in situ observations of auroral particle acceleration and related phenomena. In a large number of the orbits, auroral kilometric radiation (AKR) was observed, and in approximately 35 orbits the satellite passed through AKR source regions as evidenced by very strong signals at the local electron cyclotron frequency f{sub ce}. These sources were found at the poleward edge of the auroral oval at altitudes, from 5,000 to 8,000 km, predominantly in the evening sector. The strong AKR signal has a sharp low-frequency cutoff at or very close to f{sub ce} in the source. In addition to AKR, strong broadband electrostatic noise is measured during the source crossings. Energetic (1-15 keV) electrons are always present at and around the AKR sources. Upward directed ion beams of several keV are closely correlated with the source as are strong and variable electric fields, indicating that a region of upward pointing electric field below the observation point is a necessary condition for AKR generation. The plasma density is measured by three independent experiments and it is generally found that the density is low across the whole auroral oval. For some source crossings the three methods agree and show a density depletion (but not always confined to the source region itself), but in many cases the three measurements do not yield consistent results. The magnetic projection of the satellite passes through auroral forms during the source crossings, and the strongest AKR events seem to be connected with kinks in an arc or more complicated structures.

  5. VLBI observations of Infrared-Faint Radio Sources

    NASA Astrophysics Data System (ADS)

    Middelberg, Enno; Phillips, Chris; Norris, Ray; Tingay, Steven

    2006-10-01

    We propose to observe a small sample of radio sources from the ATLAS project (ATLAS = Australia Telescope Large Area Survey) with the LBA, to determine their compactness and map their structures. The sample consists of three radio sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubbed Infrared-Faint Radio Sources, or IFRS, is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations: we will map their structure to test whether they resemble core-jet or double-lobed morphologies, and we will measure the flux densities on long baselines, to determine their compactness. Previous snapshot-style LBA observations of two other IFRS yielded no detections, hence we propose to use disk-based recording with 512 Mbps where possible, for highest sensitivity. With the observations proposed here, we will increase the number of VLBI-observed IFRS from two to five, soon allowing us to draw general conclusions about this intriguing new class of objects.

  6. Test definitions for the evaluation of infrasound sensors.

    SciTech Connect

    Kromer, Richard Paul; Hart, Darren M.; Harris, James Mark

    2007-07-01

    Most test methodologies referenced in this Test Definition and Test Procedures were designed by Sandia specifically for geophysical instrumentation evaluation. When appropriate, test instrumentation calibration is traceable to the National Institute for Standards Technology (NIST). The objectives are to evaluate the overall technical performance of the infrasound sensor. The results of these evaluations can be compared to the manufacturer's specifications and any relevant application requirements or specifications.

  7. Numerical prediction of meteoric infrasound signatures

    NASA Astrophysics Data System (ADS)

    Nemec, Marian; Aftosmis, Michael J.; Brown, Peter G.

    2017-06-01

    We present a thorough validation of a computational approach to predict infrasonic signatures of centimeter-sized meteoroids. This is the first direct comparison of computational results with well-calibrated observations that include trajectories, optical masses and ground pressure signatures. We assume that the energy deposition along the meteor trail is dominated by atmospheric drag and simulate a steady, inviscid flow of air in thermochemical equilibrium to compute a near-body pressure signature of the meteoroid. This signature is then propagated through a stratified and windy atmosphere to the ground using a methodology from aircraft sonic-boom analysis. The results show that when the source of the signature is the cylindrical Mach-cone, the simulations closely match the observations. The prediction of the shock rise-time, the zero-peak amplitude of the waveform and the duration of the positive pressure phase are consistently within 10% of the measurements. Uncertainty in primarily the shape of the meteoroid results in a poorer prediction of the trailing part of the waveform. Overall, our results independently verify energy deposition estimates deduced from optical observations.

  8. Analysis and modeling of infrasound from a four-stage rocket launch

    DOE PAGES

    Blom, Philip Stephen; Marcillo, Omar Eduardo; Arrowsmith, Stephen

    2016-06-17

    Infrasound from a four-stage sounding rocket was recorded by several arrays within 100 km of the launch pad. Propagation modeling methods have been applied to the known trajectory to predict infrasonic signals at the ground in order to identify what information might be obtained from such observations. There is good agreement between modeled and observed back azimuths, and predicted arrival times for motor ignition signals match those observed. The signal due to the high-altitude stage ignition is found to be low amplitude, despite predictions of weak attenuation. As a result, this lack of signal is possibly due to inefficient aeroacousticmore » coupling in the rarefied upper atmosphere.« less

  9. Impact of mountain gravity waves on infrasound propagation

    NASA Astrophysics Data System (ADS)

    Damiens, Florentin; Lott, François; Millet, Christophe

    2016-04-01

    Linear theory of acoustic propagation is used to analyze how mountain waves can change the characteristics of infrasound signals. The mountain wave model is based on the integration of the linear inviscid Taylor-Goldstein equation forced by a nonlinear surface boundary condition. For the acoustic propagation we solve the wave equation using the normal mode method together with the effective sound speed approximation. For large-amplitude mountain waves we use direct numerical simulations to compute the interactions between the mountain waves and the infrasound component. It is shown that the mountain waves perturb the low level waveguide, which leads to significant acoustic dispersion. The mountain waves also impact the arrival time and spread of the signals substantially and can produce a strong absorption of the wave signal. To interpret our results we follow each acoustic mode separately and show which mode is impacted and how. We also show that the phase shift between the acoustic modes over the horizontal length of the mountain wave field may yield to destructive interferences in the lee side of the mountain, resulting in a new form of infrasound absorption. The statistical relevance of those results is tested using a stochastic version of the mountain wave model and large enough sample sizes.

  10. In-situ comparison calibration of infrasound array elements

    NASA Astrophysics Data System (ADS)

    Gabrielson, T. B.

    2009-12-01

    A typical infrasound array element consists of an infrasonic sensor connected to a multiple-pipe or porous-hose system for reduction of wind noise. While the frequency response of the sensor itself may be known, the wind-noise reduction system can modify that response. One approach to measuring the actual frequency response in situ is to perform a comparison calibration using ambient noise. The reference sensor must have a sufficiently low self noise and have a well characterized frequency response over the band of interest. In the cases presented here, three reference sensors are placed and summed to form a virtual reference at the geometric center of the pipe system. Under low-wind conditions, coherence between the virtual reference and the infrasound element is typically greater than 0.8 from 0.01 to 8 Hz. Proper combination of auto- and cross-spectral averages over a several-hour period produces an estimate of the response of the infrasound system relative to that of the virtual reference. Measured coherence and the consistency between the magnitude and the phase provide quality checks on the process. [Funded by the US Army Space and Missile Defense Command

  11. Further observations of the burst source MXB 1728-34

    NASA Technical Reports Server (NTRS)

    Hoffman, J. A.; Lewin, W. H. G.; Doty, J.

    1977-01-01

    MXB 1728-34 has been observed by the SAS 3 observatory on eight occasions. It was bursting 95-100 per cent of the time, with burst intervals from 4 to 8 hr. The burst intervals were not correlated with the burst intensities. Seven relatively hard bursts occurring in July 1976 were all observed at energies up to about 30 keV. Following each of these bursts, enhanced X-ray emission was observed for several minutes, with a much softer spectrum than that of the bursts themselves. No periodic pulsations were observed from the associated steady source.

  12. Radio observations in the fields of COS-B gamma ray sources. IV - First quadrant sources

    NASA Technical Reports Server (NTRS)

    Ozel, M. E.; Schlickeiser, R.; Sieber, W.; Younis, S.

    1988-01-01

    The field of five COS-B gamma-ray sources in the first galactic quadrant have been mapped using the Effelsberg radio telescope at several frequencies. Candidate objects as potential radio counterparts of gamma-ray sources are discussed in the light of current observations; however, mostly being due to the crowded nature of the radio fields, no clear identification has been possible.

  13. Radio observations in the fields of COS-B gamma ray sources. IV - First quadrant sources

    NASA Technical Reports Server (NTRS)

    Ozel, M. E.; Schlickeiser, R.; Sieber, W.; Younis, S.

    1988-01-01

    The field of five COS-B gamma-ray sources in the first galactic quadrant have been mapped using the Effelsberg radio telescope at several frequencies. Candidate objects as potential radio counterparts of gamma-ray sources are discussed in the light of current observations; however, mostly being due to the crowded nature of the radio fields, no clear identification has been possible.

  14. Design and Development of a High Impedance Amplifier For Use With Piezoelectric Infrasound Microphones

    NASA Astrophysics Data System (ADS)

    Kleinert, D. E.; Talmadge, C. L.

    2011-12-01

    The National Center for Physical Acoustics (NCPA) has developed a new class of high fidelity low cost piezoelectric infrasound sensors. One of the key electronic issues has been the design and development of the appropriate high impedance amplifiers including material specification as well as circuit layout and fabrication. The high impedance amplifier is required to allow the piezoelectronic sensor to operate over its entire bandwidth as the sensor itself has high impedance at the low frequency end of its operation. The specifications include a flat frequency response from at least .01 Hz to 500 Hz, a dynamic range suitable to feed a 24 bit ADC and reasonably low power (mW levels). There has been extensive field testing of the resulting amplifier in conjunction with the piezoelectric microphone, also developed at NCPA, in a variety of locations and climates using various sources, including hurricanes, tornados and high explosive detonations.

  15. Multiwavelength observations of unidentified high energy gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1995-01-01

    As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with catalogued objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. This two year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x-ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. This second year was devoted to studies of unidentified gamma-ray sources from the first EGRET catalog, similar to previous observations. Efforts have concentrated on the sources at low and intermediate Galactic latitudes, which are the most plausible pulsar candidates.

  16. Type III source locations as inferred from stereoscopic observations

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Y.; Lammer, Helmut; Al-Haddad, Eimad; Hammoud, Muhamed; Galopeau, Patrick H. M.; Lichtenegger, Herbert

    2017-04-01

    We study the Type III solar bursts simultaneously recorded by radio experiments onboard Cassini, Ulysses and Wind. Those radio bursts cover a large frequency range from about 14 MHz to a few kHz. The corresponding source locations are mainly in the solar corona and the interplanetary medium. The empirical electron density models provide different distances depending on the emission mode, fundamental or harmonic. A real trouble arises due to the distance discrepancies, as inferred from the models. Also the Archimedean spiral trajectories of the electrons, at the origin of the Type III bursts, are another difficulty to correctly estimate the source locations. We show in our analysis that the stereoscopic observations are essential to reduce the source location inaccuracy. We finally discuss the relationship between the Type III beams, the emission modes and the source locations.

  17. Using Seismic and Infrasonic Data to Identify Persistent Sources

    NASA Astrophysics Data System (ADS)

    Nava, S.; Brogan, R.

    2014-12-01

    Data from seismic and infrasound sensors were combined to aid in the identification of persistent sources such as mining-related explosions. It is of interest to operators of seismic networks to identify these signals in their event catalogs. Acoustic signals below the threshold of human hearing, in the frequency range of ~0.01 to 20 Hz are classified as infrasound. Persistent signal sources are useful as ground truth data for the study of atmospheric infrasound signal propagation, identification of manmade versus naturally occurring seismic sources, and other studies. By using signals emanating from the same location, propagation studies, for example, can be conducted using a variety of atmospheric conditions, leading to improvements to the modeling process for eventual use where the source is not known. We present results from several studies to identify ground truth sources using both seismic and infrasound data.

  18. Modeling of Jovian Hectometric Radiation Source Locations: Ulysses Observations

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Reiner, M. J.

    1996-01-01

    The Unified Radio and Plasma Wave (URAP) experiment on Ulysses has provided unique high latitude measurements of Jovian hectometric radiation (HOM) during its encounter with Jupiter in February 1992. URAP was the first radio instrument in the Jovian environment with radio direction-finding capability, which was previously used to determine the HOM source locations in the Jovian magnetosphere. These initial source location determinations were based on several assumptions, including the neglect of refractive effects, which may be tested. We have, for the first time, combined the measured incident ray-direction at the spacecraft with a model magnetosphere to directly trace the rays back to the HOM source. We concentrate on the observations of HOM from high northern latitudes when Ulysses was at distances less than 15 R(sub j). The three- dimensional ray-tracing calculations presented here indicate that the HOM sources probably lie on L shells in the range 3 less than or approximately equal to L less than 7 (tilted dipole magnetic field model) consistent with previous determinations that ignored the effects of refraction. The ray-tracing results, however, indicate that wave refraction due to the Io torus and the magnetic field can significantly influence the precise source location. We show that constraints on the locations imposed by the gyroemission mechanism suggest that the lo torus density may have experienced temporal and/or spatial fluctuations during the Ulysses observations of HOM. Finally, in the cold plasma approximation we demonstrate that even if the emission were nearly linearly polarized near the source region, almost circular polarization will be observed at Ulysses, in agreement with observations.

  19. Infrasound Sensor and Porous-Hose Filter Characterization Results

    NASA Astrophysics Data System (ADS)

    Hart, D. M.; Harris, J. M.

    2008-12-01

    The Ground-Based Nuclear Explosion Monitoring Research and Development (GNEM R&D) program at Sandia National Laboratories (SNL) is regarded as the primary center for unbiased expertise in testing and evaluation of geophysical sensors and instrumentation for nuclear explosion monitoring. Over the past year much of our work has focused in the area of infrasound sensor characterization through the continuing development of an infrasound sensor characterization test-bed. Our main areas of focus have been in new sensor characterization and understanding the effects of porous-hose filters for reducing acoustic background signals. Three infrasound sensors were evaluated for characteristics of instrument response, linearity and self-noise. The sensors tested were Chaparral Physics model 2.5 low-gain, New Mexico Tech All-Sensor and the Inter-Mountain Labs model SS avalanche sensor. For the infrasound sensors tested, the test results allow us to conclude that two of the three sensors had sufficiently quiet noise floor to be at or below the Acoustic low-noise model from 0.1 to 7 Hz, which make those sensors suitable to explosion monitoring. The other area of focus has been to understand the characteristics of porous-hose filters used at some monitoring sites. For this, an experiment was designed in which two infrasound sensors were co- located. One sensor was connected to a typical porous-hose spatial filter consisting of eight individual hoses covering a 30m aperture and the second sensor was left open to unimpeded acoustic input. Data were collected for several days, power spectrum computed for two-hour windows and the relative gain of the porous-hose filters were estimated by dividing the power spectrum. The porous-hose filter appears to attenuate less than 3 dB (rel 1 Pa**2/Hz) below 0.1 Hz and as much as 25 dB at 1 Hz and between 20 to 10 dB above 10 Hz. Several more experiments will be designed to address the effects of different characteristics of the individual porous

  20. Commercial observation satellites: broadening the sources of geospatial data

    NASA Astrophysics Data System (ADS)

    Baker, John C.; O'Connell, Kevin M.; Venzor, Jose A.

    2002-09-01

    Commercial observation satellites promise to broaden substantially the sources of imagery data available to potential users of geospatial data and related information products. We examine the new trend toward private firms acquiring and operating high-resolution imagery satellites. These commercial observation satellites build on the substantial experience in Earth observation operations provided by government-owned imaging satellites for civilian and military purposes. However, commercial satellites will require governments and companies to reconcile public and private interests in allowing broad public access to high-resolution satellite imagery data without creating national security risks or placing the private firms at a disadvantage compared with other providers of geospatial data.

  1. A likely source of an observation report in Ptolemy's Almagest.

    NASA Astrophysics Data System (ADS)

    Jones, A.

    1999-09-01

    A recently publishes volume of Greek papyri from Oxyrhynchus (modern Bahnasa, Egypt) containing astronomical text, tables, and horoscopes also includes a fragment of a theoretical work on planetary theory. This text, published under the number P.Oxy. LXI 4133, contains the report of an observation of Jupiter's position in AD 104-105 and refers also to another observation of Jupiter made 344 years earlier. The author of the present note has identified tentatively Menelaus of Alexandria as the author of the treatise on planetary theory. Here, he argues that the recovered treatise was very likely Ptolemy's immediate source for the Jupiter observations referred to in the Almagest.

  2. Isis 1 observations at the source of auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Benson, R. F.; Calvert, W.

    1979-01-01

    Observations of auroral kilometric radiation (AKR) were made by Isis 1 in the source region. The radiation is found to be generated in the extraordinary mode just above the local cut-off frequency and to emanate nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is less than 0.2. The density depletion is restricted to altitudes above about 2000 km, and the upper AKR frequency limit corresponds to the extraordinary cut-off frequency at this altitude. AKR is observed from Isis 1 above the nighttime auroral zone over a wider extent in longitude than in latitude with an intense source region observed most often near 2200 LMT and 70 deg invariant latitude. It is directly related to inverted V electron precipitation events with an electron-to-wave energy conversion efficiency of the order of 0.1 to 1%.

  3. Isis 1 observations at the source of auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Benson, R. F.; Calvert, W.

    1979-01-01

    Observations of auroral kilometric radiation (AKR) were made by Isis 1 in the source region. The radiation is found to be generated in the extraordinary mode just above the local cut-off frequency and to emanate nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is less than 0.2. The density depletion is restricted to altitudes above about 2000 km, and the upper AKR frequency limit corresponds to the extraordinary cut-off frequency at this altitude. AKR is observed from Isis 1 above the nighttime auroral zone over a wider extent in longitude than in latitude with an intense source region observed most often near 2200 LMT and 70 deg invariant latitude. It is directly related to inverted V electron precipitation events with an electron-to-wave energy conversion efficiency of the order of 0.1 to 1%.

  4. Stellar Source Selections for Image Validation of Earth Observation Satellite

    NASA Astrophysics Data System (ADS)

    Yu, Jiwoong; Park, Sang-Young; Lim, Dongwook; Lee, Dong-Han; Sohn, Young-Jong

    2011-12-01

    A method of stellar source selection for validating the quality of image is investigated for a low Earth orbit optical remote sensing satellite. Image performance of the optical payload needs to be validated after its launch into orbit. The stellar sources are ideal source points that can be used to validate the quality of optical images. For the image validation, stellar sources should be the brightest as possible in the charge-coupled device dynamic range. The time delayed and integration technique, which is used to observe the ground, is also performed to observe the selected stars. The relations between the incident radiance at aperture and V magnitude of a star are established using Gunn & Stryker's star catalogue of spectrum. Applying this result, an appropriate image performance index is determined, and suitable stars and areas of the sky scene are selected for the optical payload on a remote sensing satellite to observe. The result of this research can be utilized to validate the quality of optical payload of a satellite in orbit.

  5. Center determination for trailed sources in astronomical observation images

    NASA Astrophysics Data System (ADS)

    Du, Jun Ju; Hu, Shao Ming; Chen, Xu; Guo, Di Fu

    2014-11-01

    Images with trailed sources can be obtained when observing near-Earth objects, such as small astroids, space debris, major planets and their satellites, no matter the telescopes track on sidereal speed or the speed of target. The low centering accuracy of these trailed sources is one of the most important sources of the astrometric uncertainty, but how to determine the central positions of the trailed sources accurately remains a significant challenge to image processing techniques, especially in the study of faint or fast moving objects. According to the conditions of one-meter telescope at Weihai Observatory of Shandong University, moment and point-spread-function (PSF) fitting were chosen to develop the image processing pipeline for space debris. The principles and the implementations of both two methods are introduced in this paper. And some simulated images containing trailed sources are analyzed with each technique. The results show that two methods are comparable to obtain the accurate central positions of trailed sources when the signal to noise (SNR) is high. But moment tends to fail for the objects with low SNR. Compared with moment, PSF fitting seems to be more robust and versatile. However, PSF fitting is quite time-consuming. Therefore, if there are enough bright stars in the field, or the high astronometric accuracy is not necessary, moment is competent. Otherwise, the combination of moment and PSF fitting is recommended.

  6. Infrasound Generation from the HH Seismic Hammer.

    SciTech Connect

    Jones, Kyle Richard

    2014-10-01

    The HH Seismic hammer is a large, "weight-drop" source for active source seismic experiments. This system provides a repetitive source that can be stacked for subsurface imaging and exploration studies. Although the seismic hammer was designed for seismological studies it was surmised that it might produce energy in the infrasonic frequency range due to the ground motion generated by the 13 metric ton drop mass. This study demonstrates that the seismic hammer generates a consistent acoustic source that could be used for in-situ sensor characterization, array evaluation and surface-air coupling studies for source characterization.

  7. Classification, Characterization, and Automatic Detection of Volcanic Explosion Complexity using Infrasound

    NASA Astrophysics Data System (ADS)

    Fee, D.; Matoza, R. S.; Lopez, T. M.; Ruiz, M. C.; Gee, K.; Neilsen, T.

    2014-12-01

    Infrasound signals from volcanoes represent the acceleration of the atmosphere during an eruption and have traditionally been classified into two end members: 1) "explosions" consisting primarily of a high amplitude bi-polar pressure pulse that lasts a few to tens of seconds, and 2) "tremor" or "jetting" consisting of sustained, broadband infrasound lasting for minutes to hours. However, as our knowledge and recordings of volcanic eruptions have increased, significant infrasound signal diversity has been found. Here we focus on identifying and characterizing trends in volcano infrasound data to help better understand eruption processes. We explore infrasound signal metrics that may be used to quantitatively compare, classify, and identify explosive eruptive styles by systematic analysis of the data. We analyze infrasound data from short-to-medium duration explosive events recorded during recent infrasound deployments at Sakurajima Volcano, Japan; Karymsky Volcano, Kamchatka; and Tungurahua Volcano, Ecuador. Preliminary results demonstrate that a great variety of explosion styles and flow behaviors from these volcanoes can produce relatively similar bulk acoustic waveform properties, such as peak pressure and event duration, indicating that accurate classification of physical eruptive styles requires more advanced field studies, waveform analyses, and modeling. Next we evaluate the spectral and temporal properties of longer-duration tremor and jetting signals from large eruptions at Tungurahua Volcano; Redoubt Volcano, Alaska; Augustine Volcano, Alaska; and Nabro Volcano, Eritrea, in an effort to identify distinguishing infrasound features relatable to eruption features. We find that unique transient signals (such as repeated shocks) within sustained infrasound signals can provide critical information on the volcanic jet flow and exhibit a distinct acoustic signature to facilitate automatic detection. Automated detection and characterization of infrasound associated

  8. Deriving daily and seasonal variations in meteorological gravity wave parameters from a tropical infrasound station and comparisons with lightning strike data form ATDnet and TRMM LIS.

    NASA Astrophysics Data System (ADS)

    Marlton, Graeme; Charlton-Perez, Andrew; Harrison, Giles

    2017-04-01

    A wealth of work has shown that meteorological gravity wave parameters can be derived from both satellite data and weather balloons. Satellite data has good temporal and spatial coverage but can only probe the lower stratosphere and mesosphere. Radiosonde wind and temperature profiles can also be used to infer gravity wave information in the upper troposphere and lower stratosphere. Both methods have been used to investigate seasonal variations in gravity wave parameters at these heights. However, these methods cannot be used to infer gravity wave parameters near the surface. One method to detect atmospheric gravity waves at the surface is by using an infrasound array. Infrasound arrays consist of several microbarometers which are spaced kilometres apart. As the wave passes over the array subtle pressure perturbations are subsequently detected at each microbarometer. The temporal differences in each microbarometer's time series allow a gravity wave's velocity, back azimuth, ground based frequency and amplitude to be calculated using the progressive multichannel correlation method. In order to calculate further meteorological values such as wave number, velocity perturbations and hence find the momentum flux for each gravity wave, data from meteorological station in close proximity to the array need to be combined with the infrasound data, which is explored here. Gravity wave parameters calculated from infra sound data combined with meteorological data over several years will be shown for a station (IS17) in the Ivory Coast. Blanc et al 2010 showed an annual variation in gravity wave back azimuth due to the shifting of thunderstorms associated with the ITCZ. A spectral analysis of all gravity wave parameters has revealed daily and seasonal variations, which are further explored. To further understand the seasonal variations observed data from the Tropical Rainfall Measurement Mission (TRMM) rainfall estimate and TRMM LIS lightning data are used to relate how the

  9. Dynamics of the Bingham Canyon rock avalanches (Utah, USA) resolved from topographic, seismic, and infrasound data

    NASA Astrophysics Data System (ADS)

    Moore, Jeffrey R.; Pankow, Kristine L.; Ford, Sean R.; Koper, Keith D.; Hale, J. Mark; Aaron, Jordan; Larsen, Chris F.

    2017-03-01

    The 2013 Bingham Canyon Mine rock avalanches represent one of the largest cumulative landslide events in recorded U.S. history and provide a unique opportunity to test remote analysis techniques for landslide characterization. Here we combine aerial photogrammetry surveying, topographic reconstruction, numerical runout modeling, and analysis of broadband seismic and infrasound data to extract salient details of the dynamics and evolution of the multiphase landslide event. Our results reveal a cumulative intact rock source volume of 52 Mm3, which mobilized in two main rock avalanche phases separated by 1.5 h. We estimate that the first rock avalanche had 1.5-2 times greater volume than the second. Each failure initiated by sliding along a gently dipping (21°), highly persistent basal fault before transitioning to a rock avalanche and spilling into the inner pit. The trajectory and duration of the two rock avalanches were reconstructed using runout modeling and independent force history inversion of intermediate-period (10-50 s) seismic data. Intermediate- and shorter-period (1-50 s) seismic data were sensitive to intervals of mass redirection and constrained finer details of the individual slide dynamics. Back projecting short-period (0.2-1 s) seismic energy, we located the two rock avalanches within 2 and 4 km of the mine. Further analysis of infrasound and seismic data revealed that the cumulative event included an additional 11 smaller landslides (volumes 104-105 m3) and that a trailing signal following the second rock avalanche may result from an air-coupled Rayleigh wave. Our results demonstrate new and refined techniques for detailed remote characterization of the dynamics and evolution of large landslides.

  10. Diagnosing Tibetan pollutant sources via volatile organic compound observations

    NASA Astrophysics Data System (ADS)

    Li, Hongyan; He, Qiusheng; Song, Qi; Chen, Laiguo; Song, Yongjia; Wang, Yuhang; Lin, Kui; Xu, Zhencheng; Shao, Min

    2017-10-01

    Atmospheric transport of black carbon (BC) from surrounding areas has been shown to impact the Tibetan environment, and clarifying the geographical source and receptor regions is crucial for providing guidance for mitigation actions. In this study, 10 trace volatile organic compounds (VOCs) sampled across Tibet are chosen as proxies to diagnose source regions and related transport of pollutants to Tibet. The levels of these VOCs in Tibet are higher than those in the Arctic and Antarctic regions but much lower than those observed at many remote and background sites in Asia. The highest VOC level is observed in the eastern region, followed by the southern region and the northern region. A positive matrix factorization (PMF) model found that three factors-industry, biomass burning, and traffic-present different spatial distributions, which indicates that different zones of Tibet are influenced by different VOC sources. The average age of the air masses in the northern and eastern regions is estimated to be 3.5 and 2.8 days using the ratio of toluene to benzene, respectively, which indicates the foreign transport of VOC species to those regions. Back-trajectory analyses show that the Afghanistan-Pakistan-Tajikistan region, Indo-Gangetic Plain (IGP), and Meghalaya-Myanmar region could transport industrial VOCs to different zones of Tibet from west to east. The agricultural bases in northern India could transport biomass burning-related VOCs to the middle-northern and eastern zones of Tibet. High traffic along the unique national roads in Tibet is associated with emissions from local sources and neighboring areas. Our study proposes international joint-control efforts and targeted actions to mitigate the climatic changes and effects associated with VOCs in Tibet, which is a climate sensitive region and an important source of global water.

  11. Optical observations of lensing candidates for millimeter-wave sources

    NASA Astrophysics Data System (ADS)

    Blackman, Ryan; Hughes, J. P.

    2014-01-01

    The field of observational cosmology has taken great strides forward with the development of large aperture, ground-based telescopes that can perform large area surveys in millimeter wavelengths, such as the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT). These instruments have provided astronomers with a new window on the distant universe, from the Cosmic Microwave Background to more nearby active galaxies and dusty star forming galaxies. Recently it was found that a significant subset of the millimeter sources discovered in the new surveys are magnified by foreground galaxies or galaxy clusters acting as gravitational lenses. Therefore, finding and measuring the properties of these lenses is an important aspect of millimeter observing, and a critical step is to obtain their spectroscopic redshifts. We identified 6 lensing candidates for sources observed in an SPT survey using optical imaging data from the Blanco 4-meter telescope. These were then targeted for spectroscopic observations using the Southern African Large Telescope (SALT) from late 2011 to early 2013. From these data we were able to determine the redshift of each candidate, obtaining a range of values from z=0.14 to z=0.80. This project was funded by a grant from the National Science Foundation (PHY-1263280) under the Research Experiences for Undergraduates (REU) program to Rutgers University.

  12. Chandra Observations of Dying Radio Sources in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-01-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims. We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods. We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results. The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions. We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  13. Chandra observations of dying radio sources in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-12-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims: We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods: We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results: The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions: We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  14. Ionosonde tracking of infrasound wavefronts in the thermosphere launched by seismic waves after the 2010 M8.8 Chile earthquake

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Yusupov, Kamil; Akchurin, Adel

    2015-04-01

    It is well known that atmospheric waves excited by intense earthquakes induce ionospheric disturbances. At remote distances greater than ~500 km, Rayleigh waves are the major source of infrasounds that propagate upward in the atmosphere. Acoustic waves interact with the ionospheric plasma through collision between neutral particles and ions. Ionospheric disturbances caused by Rayleigh waves near the low frequency part of the Airy phase (a period of several minutes) are detected as a change in the total electron content since the wavelength of induced acoustic waves in the thermosphere is comparable to the ionospheric slab thickness. On the other hand, Rayleigh waves near the high frequency part of the Airy phase (a period of several tens of seconds) cause distortion of ionogram traces characterized by a multiple cusp signature (MCS). The vertical separation of the ledge corresponding to each cusp is the wavelength of the infrasound in the thermosphere. Thus, the MCS ionogram is considered to be a snapshot of the wave that propagates upward. We conducted rapid run operation of ionosonde with a frame rate of 1 min at Kazan, Russia. After the 2010 M8.8 Chile earthquake (epicentral distance was 15,162 km), ionospheric disturbances showing MCSs on ionograms were observed for several tens of minutes. The sound speed calculated by a model was 500~700 m/s at the height of the bottomside ionosphere and wavefronts should propagate 30~42 km upward during the intervals of ionograms, which is smaller than the bottomside depth of the ionosphere. The seismogram obtained at Obninsk near Moscow, Russia (epicentral distance was 14,369 km) recorded Rayleigh waves with a period of ~17 s responsible for the ionospheric disturbances showing MCS, when the plot was shifted by the time corresponding to the difference of epicentral distances between the two locations by assuming a Rayleigh wave speed of 3 km/s. The vertical wavelength of the acoustic waves launched by the Rayleigh waves was

  15. Infrasound in the Zone of Silence

    DTIC Science & Technology

    2008-09-01

    array was installed at 288 km from the source, north of Gerlach, NV ( GERL ). The locations of the temporary arrays and the individual layouts are shown in...Technologies 895 NV02 NV01 NV03 NV04 1000 m Site 1 Site 2 Site 3 Site 4 50 m FALN FALS SHURZ NEW BOMB NVIAR GERL 2007 only 2006 and 2007 Source 2006 only...conditions were significantly higher. GERL recorded a combination of stratospheric and thermospheric arrivals (celerities of 296 for stratospheric and

  16. Hardware design document for the Infrasound Prototype for a CTBT IMS station

    SciTech Connect

    Breding, D.R.; Kromer, R.P.; Whitaker, R.W.; Sandoval, T.

    1997-11-01

    The Hardware Design Document (HDD) describes the various hardware components used in the Comprehensive Test Ban Treaty (CTBT) Infrasound Prototype and their interrelationships. It divides the infrasound prototype into hardware configurations items (HWCIs). The HDD uses techniques such as block diagrams and parts lists to present this information. The level of detail provided in the following sections should be sufficient to allow potential users to procure and install the infrasound system. Infrasonic monitoring is a low cost, robust, and effective technology for detecting atmospheric explosions. Low frequencies from explosion signals propagate to long ranges (few thousand kilometers) where they can be detected with an array of sensors.

  17. Observation of nonlinear resonances in the advanced light source

    NASA Astrophysics Data System (ADS)

    Robin, D.; Collins, H.; Decking, W.; Portmann, G.; Schachinger, L.; Zholents, A.

    1994-09-01

    Observations of nonlinear resonances in the Advanced Light Source have been made by scanning betatron tunes and observing count rates in a beam-loss radiation monitor placed down stream of a beam scraper. The authors have found that it is possible to see structural resonances which are unallowed as well as those which are allowed by the ring's natural 12-fold symmetry. By systematically breaking the amount of symmetry they see that the widths of the unallowed resonances grow while the widths of the allowed resonances do not. In this paper the authors briefly discuss the importance of symmetry and its effect on resonances in the design of the ALS. Next they describe their experimental setup and discuss the performance of the beam loss monitor which they used to view the resonances. They then present scans of the tune space where one can see the presence of the structural resonances and their evolution when the lattice symmetry is systematically broken.

  18. Observation of nonlinear resonances in the advanced light source

    NASA Astrophysics Data System (ADS)

    Robin, D.; Collins, H.; Decking, W.; Portmann, G.; Schachinger, L.; Zholents, A.

    1995-09-01

    Observations of nonlinear resonances in the Advanced Light Source have been made by scanning betatron tunes and observing count rates in a beam-loss radiation monitor placed down stream of a beam scraper. We have found that it is possible to see structural resonances which are unallowed as well as those which are allowed by the ring's natural 12-fold symmetry. By systematically breaking the amount of symmetry we see that the widths of the unallowed resonances grow while the widths of the allowed resonances do not. In this paper we briefly discuss the importance of symmetry and its effect on resonances in the design of the ALS. Next we describe our experimental setup and discuss the performance of the beam loss monitor which we used to view the resonances. We then present scans of the tune space where one can see the presence of the structural resonances and their evolution when the lattice symmetry is systematically broken.

  19. Sources of Mass and Energy Observed in Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Riofrio, L. M.

    2005-12-01

    EVIDENCE from the laboratory of Saturn's Rings solves riddles of planet formation. Observations by Cassini and other spacecraft show conditions similiar to the birth of our Solar System. These observations lead to new theories of small-body accretion. Applications have benefits for physics and energy on Earth. There have been several open questions regarding the planets. Most puzzling is the formation of mountain-sized planetesimals from protostellar dust, for these objects could not form naturally. Power source of the "dynamo" generating planetary magnetic fields was also unknown. Internal heat generated by planets and even small moons is an additional mystery. These riddles may be explained by presence of primordial singularities in the Solar System's formation. Saturn's Rings are a field of ice in which the tracks of these objects may be seen. The Cassini spacecraft has returned many fascinating images of the Rings. We now know them to be home to massive unseen objects. Satellite objects glimpsed in the Encke and Keeler gaps show behaviour unlike moons of rock or ice. Discrete trails of dirt and molecular oxygen indicate radiation discharge emanating from these objects. Similiar trails photographed in Cassini's Division indicate massive objects where no large object has been sighted visually. We must consider whether the Rings could be a home to singularities. It is generally agreed the primordial singularities were created shortly after the Big Bang, and exist in unknown numbers today. Presence of these objects in the Solar System's formation would have seeded formation of planetesimals and larger bodies. Their hidden presence would explain both planetary magnetic fields and internal heat sources. They would also explain the Ring's presence and longetivity. The most convincing evidence for singularities would be radiation discharge. Observation of a polar "hot spot" on Enceladus can not be explained by old theories of radioactive decay. The only feasible source

  20. Further observations of new sources in the AFCRL survey. [infrared sources

    NASA Technical Reports Server (NTRS)

    Kleinmann, S. G.

    1977-01-01

    Salient aspects of follow-up observations carried out on new sources discovered earlier in the AFCRL rocket IR sky survey are summarized. Ground-based searches, studies of class properties of the new AFCRL sources (galactic distribution, IR spectra, time variation), and closer examination of some 'unusual objects' are discussed. Brief descriptions are offered of some unusual objects: possible protostars, and specifically CRL 877; H2O masers in the Mon R2 cloud; the Egg Nebula (CRL 2688); CRL 618, with featureless IR spectrum and optical spectrum reminiscent of a planetary nebula; CRL 437 and other objects associated with multiple-reflection nebulae.

  1. Ground-coupled air waves and diffracted infrasounds from the Arequipa earthquake of June 23, 2001

    NASA Astrophysics Data System (ADS)

    Lepichon, A.; Guilbert, J.; Van de Walle, M.

    2001-12-01

    On June 23, 2001, a strong earthquake measuring Ms 8.2 occurred along the coast of south-central Peru. This event was detected by the IS08 infrasound station of Bolivia operating for the CTBTO(Comprehensive Test Ban Treaty Organization). Coherent infrasonic waves have been detected over a period of one hour. In the first part of the signals, the analysis of the seismic coupled-air waves shows clearly that the rupture propagates from the northwertern to the southeastern part of the fault. The Doppler effect allows us to fixe the velocity of the rupture equal to 3.4 +/- 0.5 km.s-1. In the second part of the signals, the azimuth variation is interpreted as a distribution of secondary sources along the highest mountain ranges generating distant air-coupled waves in the atmosphere. The predominant source mechanism of the earthquake and two main aftershocks is likely diffracted pressure waves radiated along the Eastern Andean Cordillera from the southwest of the station to the coastline near Pamana. From the wave azimuth and arrival time determination, the horizontal scale size of the distant source regions remote from the epicenters is reconstructed over distances greater than 400 km. The generation of pressure waves associated with offshore source regions is also considered.

  2. Sound, infrasound, and sonic boom absorption by atmospheric clouds.

    PubMed

    Baudoin, Michaël; Coulouvrat, François; Thomas, Jean-Louis

    2011-09-01

    This study quantifies the influence of atmospheric clouds on propagation of sound and infrasound, based on an existing model [Gubaidulin and Nigmatulin, Int. J. Multiphase Flow 26, 207-228 (2000)]. Clouds are considered as a dilute and polydisperse suspension of liquid water droplets within a mixture of dry air and water vapor, both considered as perfect gases. The model is limited to low and medium altitude clouds, with a small ice content. Four physical mechanisms are taken into account: viscoinertial effects, heat transfer, water phase changes (evaporation and condensation), and vapor diffusion. Physical properties of atmospheric clouds (altitude, thickness, water content and droplet size distribution) are collected, along with values of the thermodynamical coefficients. Different types of clouds have been selected. Quantitative evaluation shows that, for low audible and infrasound frequencies, absorption within clouds is several orders of magnitude larger than classical absorption. The importance of phase changes and vapor diffusion is outlined. Finally, numerical simulations for nonlinear propagation of sonic booms indicate that, for thick clouds, attenuation can lead to a very large decay of the boom at the ground level.

  3. H2CO Observations Towards CH3OH Maser Sources

    NASA Astrophysics Data System (ADS)

    Okoh, Daniel; Esimbek, Jarken; Zhou, JianJun; Tang, Xindi; Chukwude, Augustine; Urama, Johnson; Okeke, Pius

    2013-03-01

    Formaldehyde (H2CO) is an accurate probe of physical conditions in dense and low-temperature molecular clouds towards massive star formation regions, while 6.7 GHz methanol (CH3OH) masers provide ideal sites to probe the earliest stages of massive stellar formation. We present preliminary results of our investigation into the possible relationship between formaldehyde and methanol astrophysical masers with the view to expanding knowledge on massive star formation processes. Observations are done using the Nanshan 25m radio telescope of the Xinjiang Astronomical Observatories, Urumqi, China. 127 Methanol sources (from the work of Green et al. 2010, Xu et al. 2003, Pestalozzi et al. 2005, and Xu et al. 2009) have been observed so far for 4.8 GHz formaldehyde absorption lines, and H2CO signals have been detected in 86 of them, 31 of which are newly discovered. We obtained good correlation (0.85 correlation coefficient) between the velocities of the sources, and a poor correlation (-0.03 correlation coefficient) between their intensities, an indication that signals from the two lines originate from about the same region, but that the excitation mechanisms that drive them are likely different.

  4. A study of infrasound propagation based on high-order finite difference solutions of the Navier-Stokes equations.

    PubMed

    Marsden, O; Bogey, C; Bailly, C

    2014-03-01

    The feasibility of using numerical simulation of fluid dynamics equations for the detailed description of long-range infrasound propagation in the atmosphere is investigated. The two dimensional (2D) Navier Stokes equations are solved via high fidelity spatial finite differences and Runge-Kutta time integration, coupled with a shock-capturing filter procedure allowing large amplitudes to be studied. The accuracy of acoustic prediction over long distances with this approach is first assessed in the linear regime thanks to two test cases featuring an acoustic source placed above a reflective ground in a homogeneous and weakly inhomogeneous medium, solved for a range of grid resolutions. An atmospheric model which can account for realistic features affecting acoustic propagation is then described. A 2D study of the effect of source amplitude on signals recorded at ground level at varying distances from the source is carried out. Modifications both in terms of waveforms and arrival times are described.

  5. ULF waves in other magnetospheres - observations and possible source mechanisms

    NASA Technical Reports Server (NTRS)

    Khurana, K. K.

    1993-01-01

    Five other planets besides the Earth (Mercury, Jupiter, Saturn, Uranus and Neptune) in our solar system are now known to possess internal magnetic fields. The exploration of these planets by the Mariner, Pioneer, Voyager and Ulysses spacecraft has revealed that all of them possess fully expressed magnetospheres which share several similarities in their structures with the Earth's magnetosphere. This paper presents an overview of the work done so far in the field of the ULF waves in the magnetospheres of Mercury, Jupiter, Saturn and Uranus. To give an idea of the expected wave periods, gyroperiods of the dominant ion species and the fundamental periods of the standing Alfven waves are presented as functions of L parameter in these magnetospheres. In the magnetosphere of Mercury, ULF waves were observed in the vicinity of the magnetopause and in the inner magnetosphere with frequencies in the range of 0.1-0.5 Hz. In the magnetosphere of Jupiter, at least three different types of wave sources are observed. Near the dayside and the dawn magnetopause, waves with periods 5-20 min and amplitudes between 5 and 10 nT are observed which may be caused by an interaction between the corotating outflowing plasma and the antisunward moving plasma from the magnetosheath. In Saturn's magnetosphere, ULF waves have been observed to be strongly confined to the plasma sheet and have wave periods in the range of 5-60 minutes. The calculated fundamental has a wave period of 5-6 hours in the region where these waves were observed. The ULF waves have extremely small amplitudes (approximately = 0.3 nT) in the magnetosphere of Uranus. These waves were also seen to be confined to the low magnitude latitudes and have periods much shorter than that of the fundamental of a standing Alfven wave.

  6. Mapping thunder sources by inverting acoustic and electromagnetic observations

    NASA Astrophysics Data System (ADS)

    Anderson, J. F.; Johnson, J. B.; Arechiga, R. O.; Thomas, R. J.

    2014-12-01

    We present a new method of locating current flow in lightning strikes by inversion of thunder recordings constrained by Lightning Mapping Array observations. First, radio frequency (RF) pulses are connected to reconstruct conductive channels created by leaders. Then, acoustic signals that would be produced by current flow through each channel are forward modeled. The recorded thunder is considered to consist of a weighted superposition of these acoustic signals. We calculate the posterior distribution of acoustic source energy for each channel with a Markov Chain Monte Carlo inversion that fits power envelopes of modeled and recorded thunder; these results show which parts of the flash carry current and produce thunder. We examine the effects of RF pulse location imprecision and atmospheric winds on quality of results and apply this method to several lightning flashes over the Magdalena Mountains in New Mexico, USA. This method will enable more detailed study of lightning phenomena by allowing researchers to map current flow in addition to leader propagation.

  7. Observational evidence for extraterrestrial gamma-ray line sources

    NASA Technical Reports Server (NTRS)

    Jacobson, A. S.; Ling, J. C.; Mahoney, W. A.; Willett, J. B.

    1978-01-01

    During the 1974 balloon flight of a high spectral resolution gamma-ray telescope, observing in the energy range of about 50 keV to 10 Mev, evidences were gathered for two cosmic sources of gamma-ray lines. These are a 73 keV line feature superimposed on a power law continuum spectrum in the 55 to 300 keV range from the Crab nebula; and a flare-like event lasting about twenty minutes, during which four intense gamma-ray lines were measured at .41, 1.79, 2.22 and 5.95 MeV. The properties and operation of the detector used are described. The measured spectrum and count rate are discussed.

  8. Studies of Accreting Neutron Stars with RXTE Cycle 4 Observations: III: TOO Observations of Atoll Sources

    NASA Technical Reports Server (NTRS)

    Paciesas, William S.

    2002-01-01

    NASA Grant NAG 5-9244 provided funds for the research projects 'ASM-Triggered TOO Observations of Kilohertz Oscillations in Five Atoll Sources' and 'Further Measurements of the Kilohertz Oscillations in 4U 1705-44' approved under the Rossi X-ray Timing Explorer (RXTE) Guest Observer Program Cycle 4 and funded under the 1999 NASA Astrophysics Data Program. The principal investigator of the observing time proposals was Dr. E. C. Ford (U. of Amsterdam). The grant was funded for one year beginning 3/15/2000. The original ADP proposal was submitted by Prof. Jan van Paradijs, who passed away in 1999 before the funds were distributed. Prof. Wilham S. Padesas administered the grant during the period of performance. In spite of a wealth of observational data on the kHz QPO in low-mass X-ray binaries (LMXBs), the interpretation of this phenomenon is currently uncertain because the pairs of kHz QPO peaks and the oscillations seen in some Type I X-ray bursts are almost, but not quite, connected by a simple beat frequency relation. Further systematic studies of systems with known QPOs are required in order to better understand the phenomenon. The proposals were intended to contribute to a solution to this confusion by observing the sources as they vary over a wide range of X-ray flux. RXTE target-of-opportunity observations of six transient atoll sources, 4U 0614+09, KS 1732-260, Ser X-1, 4U 1702-42, 4U 1820-30 and 4U 1705-44 were to be performed at various flux levels based on ASM measurements.

  9. Studies of Accreting Neutron Stars with RXTE Cycle 4 Observations: III: TOO Observations of Atoll Sources

    NASA Technical Reports Server (NTRS)

    Paciesas, William S.

    2002-01-01

    NASA Grant NAG 5-9244 provided funds for the research projects 'ASM-Triggered TOO Observations of Kilohertz Oscillations in Five Atoll Sources' and 'Further Measurements of the Kilohertz Oscillations in 4U 1705-44' approved under the Rossi X-ray Timing Explorer (RXTE) Guest Observer Program Cycle 4 and funded under the 1999 NASA Astrophysics Data Program. The principal investigator of the observing time proposals was Dr. E. C. Ford (U. of Amsterdam). The grant was funded for one year beginning 3/15/2000. The original ADP proposal was submitted by Prof. Jan van Paradijs, who passed away in 1999 before the funds were distributed. Prof. Wilham S. Padesas administered the grant during the period of performance. In spite of a wealth of observational data on the kHz QPO in low-mass X-ray binaries (LMXBs), the interpretation of this phenomenon is currently uncertain because the pairs of kHz QPO peaks and the oscillations seen in some Type I X-ray bursts are almost, but not quite, connected by a simple beat frequency relation. Further systematic studies of systems with known QPOs are required in order to better understand the phenomenon. The proposals were intended to contribute to a solution to this confusion by observing the sources as they vary over a wide range of X-ray flux. RXTE target-of-opportunity observations of six transient atoll sources, 4U 0614+09, KS 1732-260, Ser X-1, 4U 1702-42, 4U 1820-30 and 4U 1705-44 were to be performed at various flux levels based on ASM measurements.

  10. Assessment of Operational Progress of NASA Langley Developed Windshield and Microphone for Infrasound

    DTIC Science & Technology

    2013-04-01

    Assessment of Operational Progress of NASA Langley Developed Windshield and Microphone for Infrasound by W.C. Kirkpatrick Alberts, II... Windshield and Microphone for Infrasound W.C. Kirkpatrick Alberts, II, Stephen M. Tenney, and John M. Noble Sensors and Electron Devices Directorate...NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) April 2013 2. REPORT TYPE Final 3. DATES COVERED (From - To) Nov 2011–Jan

  11. Long-Period Seismicity and Very-Long-Period Infrasound Driven by Shallow Magmatic Degassing at Mount Pagan, Mariana Islands

    NASA Astrophysics Data System (ADS)

    Lyons, J. J.; Haney, M. M.; Werner, C. A.; Kelly, P. J.; Patrick, M. R.; Kern, C.; Trusdell, F.

    2015-12-01

    Mount Pagan is the currently active vent on the north end of Pagan Volcano, Mariana Islands. A persistent degassing plume, LP seismicity, and VLP infrasound (iVLP) have dominated activity since at least 2013, when ground-based geophysical sensors were first installed. Direct gas sampling with a Multi-GAS sensor indicates a plume generated by a shallow magmatic system. Here we present an analysis of coupled LP and iVLP events in order to reveal the details of their source processes and how the signals are related to shallow magmatic degassing. The LP and iVLP waveform characteristics were highly stable from July 2013 - January 2014. Both events have durations of 5-20 s, occur every 1-2 minutes, and have emergent onsets. The LP events have a dominant frequency of 0.54 Hz, while the dominant frequency of the iVLP is 0.32 Hz. The delay times between the LP and iVLP arrivals show little variation during the 7-month study, indicating a stable, shallow, and nearly co-located source. Full waveform inversion of a master LP event reveals a volumetric source 60 m below and 180 m west of the summit vent. Inverting Green's functions of different geometric combinations results in a 2-crack model dominated by a subhorizontal crack intersecting a NW-SE trending dike. The extension of the modeled crack intersects the surface near the vent location. The nearly horizontal orientation of the dominant crack is likely controlled by the orientation of lava flows and pyroclastic deposits that are observed in the western wall of the cone at the LP depth. We propose that the LP seismicity is crack resonance triggered by collapse of the gas-charged upper conduit system following periodic venting. Measured and modeled pressure-velocity (P/Vz) ratios for the seismoacoustic events indicate that elastodynamic processes associated with the seismic LP cannot generate the iVLP. Thus, we model the iVLP as volume resonance of an exponential horn, based on the shape of the crater and the wavelength of

  12. Improving Infrasound Signal Detection and Event Location in the Western US Using Atmospheric Modeling

    NASA Astrophysics Data System (ADS)

    Dannemann, F. K.; Park, J.; Marcillo, O. E.; Blom, P. S.; Stump, B. W.; Hayward, C.

    2016-12-01

    Data from five infrasound arrays in the western US jointly operated by University of Utah Seismograph Station and Southern Methodist University are used to test a database-centric processing pipeline, InfraPy, for automated event detection, association and location. Infrasonic array data from a one-year time period (January 1 2012 to December 31 2012) are used. This study focuses on the identification and location of 53 ground-truth verified events produced from near surface military explosions at the Utah Test and Training Range (UTTR). Signals are detected using an adaptive F-detector, which accounts for correlated and uncorrelated time-varying noise in order to reduce false detections due to the presence of coherent noise. Variations in detection azimuth and correlation are found to be consistent with seasonal changes in atmospheric winds. The Bayesian infrasonic source location (BISL) method is used to produce source location and time credibility contours based on posterior probability density functions. Updates to the previous BISL methodology include the application of celerity range and azimuth deviation distributions in order to accurately account for the spatial and temporal variability of infrasound propagation through the atmosphere. These priors are estimated by ray tracing through Ground-to-Space (G2S) atmospheric models as a function of season and time of day using historic atmospheric characterizations from 2007 to 2013. Out of the 53 events, 31 are successfully located using the InfraPy pipeline. Confidence contour areas for maximum a posteriori event locations produce error estimates which are reduced a maximum of 98% and an average of 25% from location estimates utilizing a simple time independent uniform atmosphere. We compare real-time ray tracing results with the statistical atmospheric priors used in this study to examine large time differences between known origin times and estimated origin times that might be due to the misidentification of

  13. Tropical cyclone waves detected with infrasound sensor array

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-02-01

    The strong winds of a tropical cyclone whip up the sea surface, driving ocean waves a dozen meters high. When one such ocean wave runs into another wave that has an equal period but is traveling in the opposite direction, the interaction produces low-frequency sound waves that can be detected thousands of kilometers away. The infrasound signals produced by interacting ocean surface waves—known as microbarom—have typical frequencies around 0.2 hertz. Researchers previously determined that as a hurricane travels along its track, early waves generated by the storm will interact with those generated later on, producing a strong microbarom signal in the storm's wake. Researchers also found, however, that microbarom signals are produced by regular surface ocean behavior, including swell, surface waves, and nontropical cyclone storms.

  14. Source properties of microearthquakes revealed by near-source observation at SAFOD (Invited)

    NASA Astrophysics Data System (ADS)

    Imanishi, K.; Ellsworth, W. L.

    2010-12-01

    Near-source observation of earthquakes in deep boreholes and mines provides significant opportunities to enhance our understanding of the source properties of earthquakes. Short hypocentral distances and a high-Q environment make it possible to observe earthquake processes that cannot be seen in shallow boreholes or at the surface. The SAFOD Main Hole is a 3.2 km-deep inclined borehole that crosses the active traces of the San Andreas Fault. A 3-component 15 Hz GS-20DM geophone was deployed within the fault zone at depths between 2350 and 2750 m. Because of the close proximity to earthquake sources, we routinely observed earthquakes with Mw < 0 with high signal-to-noise ratio. Events were recorded at three different sampling rates (1000, 2000, and 4000 sps) depending on observation period (2005 - 2010). This study focuses on earthquakes with S-P time differences shorter than 0.5s, corresponding to hypocentral distance less than 3 km. Among more than 400 earthquakes, we selected 117 events classified into 35 clusters on the basis of waveform similarity at low frequencies. Selected events range in size from approximately Mw -3 to Mw 2. The dataset includes many events in three clusters that formed the SAFOD drilling target; San Francisco, Los Angeles and Hawaii named as their relative positions with respect to those cities. We determined source parameters by the Multi-Window Spectral Ratio (MWSR) method (Imanishi and Ellsworth, 2006). The key step in the method is to stack the ratios calculated from moving windows taken along the record starting with the direct waves. We confirmed that stacking better suppresses the random noise due to differences in path than single-window methods, producing a better estimate of the source spectral ratio. For Mw>-1, the calculated stress drops range between 0.1 and 100 MPa. These observations indicate that there is no breakdown in stress drop scaling for Mw>-1. The stacked spectral ratios show that corner frequencies of events for

  15. Chandra Observations of Point Sources in Abell 2255

    NASA Technical Reports Server (NTRS)

    Davis, David S.; Miller, Neal A.; Mushotzky, Richard F.

    2003-01-01

    In our search for "hidden" AGN we present results from a Chandra observation of the nearby cluster Abell 2255. Eight cluster galaxies are associated with point-like X-ray emission, and we classify these galaxies based on their X-ray, radio, and optical properties. At least three are associated with active galactic nuclei (AGN) with no optical signatures of nuclear activity, with a further two being potential AGN. Of the potential AGN, one corresponds to a galaxy with a post-starburst optical spectrum. The remaining three X-ray detected cluster galaxies consist of two starbursts and an elliptical with luminous hot gas. Of the eight cluster galaxies five are associated with luminous (massive) galaxies and the remaining three lie in much lower luminosity systems. We note that the use of X-ray to optical flux ratios for classification of X-ray sources is often misleading, and strengthen the claim that the fraction of cluster galaxies hosting an AGN based on optical data is significantly lower than the fraction based on X-ray and radio data.

  16. Spectroscopy of compact extragalactic X-ray sources. [HEAO observations

    NASA Technical Reports Server (NTRS)

    Holt, S. S.

    1980-01-01

    The X-ray spectra of compact extragalactic sources obtained from the HEAO-1 A-2 experiment and the solid-state spectrometer onboard HEAO-2 (the Einstein Observatory) are reviewed. Seyfert spectra are remarkably consistent with characteristic power-law spectra of energy index alpha = 0.7 + .1 over a dynamic range of almost 100 in both luminosity for the whole sample, and energy for individual members. Radio-quiet quasars have similar spectra, perhaps slightly steeper, for the limited sample available. New solid-state spectrometer results for NGC 4151 yield a consistent picture for the geometry of the broad-line clouds in both these related radio-quiet classes of galactic nuclei. Radio-loud objects, especially BL Lacs, are considerably more variable in spectrum as well as luminosity. Direct synchrotron and synchrotron-self-Compton components are consistent with what we observe from these objects. Finally, the role of spectroscopy in addressing the extent to which compact extragalactic nuclei might contribute to the diffuse X-ray background is discussed.

  17. Scaling Relationship Among Source Parameters of Microearthquake," From Near Source Observation in a Deep Mine

    NASA Astrophysics Data System (ADS)

    Hiramatsu, Y.; Yoshimura, M.; Furumoto, M.

    2004-12-01

    Scaling relationships among various source parameters are important clues to understand the source process. In particular the relationship between the corner frequency, fC, and the seismic moment, MO, has been investigated by many researchers. Aki(1967) investigated fC and MO using the spectra of seismic waves and reported that these parameters obeyed a relationship of MO ∝ fC-3. For small earthquakes, the breakdown of this relationship was often reported. On the other hand, no breakdown of the relationship for microearthquakes has been reported from high quality observation at deep boreholes and in a deep gold mine. We report here these scaling relationships using waveform of microearthquakes observed at the distance range of 15m to 1km. We installed nine tri-axial borehole accelerometers within 200 m along a haulage tunnel 2650m deep in Mponeng mine in South Africa from February to December in 1996. More than 25 thousand seismic events were recorded with a sampling frequency of 15 kHz and a dynamic range of 120 dB. The recording system has flat response up to 2 KHz. Among those events, we select 378 events with high S/N. We locate hypocenters assuming infinite medium with the P-wave velocity 5.5 km/s and the S-wave velocity 3.2 km/s. We calculate the green function using the discrete wavenumber integral method into account the effect of anelasticity by Takeo (1985) and determine the seismic moment and the mechanism using moment tensor inversion. We apply the omega square model by Brune (1970) to determine the corner frequency and the stress drop. Minimizing L2 norm between the observed spectra of P and S waves and the synthetic ones give the optimum source parameters. The earthquakes analyzed in this study show the constant stress drop of 0.4 ˜8MPa in the ranges of 40

  18. Near Source 2007 Peru Tsunami Runup Observations and Modeling

    NASA Astrophysics Data System (ADS)

    Borrero, J. C.; Fritz, H. M.; Kalligeris, N.; Broncano, P.; Ortega, E.

    2008-12-01

    On 15 August 2007 an earthquake with moment magnitude (Mw) of 8.0 centered off the coast of central Peru, generated a tsunami with locally focused runup heights of up to 10 m. A reconnaissance team was deployed two weeks after the event and investigated the tsunami effects at 51 sites. Three tsunami fatalities were reported south of the Paracas Peninsula in a sparsely populated desert area where the largest tsunami runup heights and massive inundation distances up to 2 km were measured. Numerical modeling of the earthquake source and tsunami suggest that a region of high slip near the coastline was primarily responsible for the extreme runup heights. The town of Pisco was spared by the Paracas Peninsula, which blocked tsunami waves from propagating northward from the high slip region. As with all near field tsunamis, the waves struck within minutes of the massive ground shaking. Spontaneous evacuations coordinated by the Peruvian Coast Guard minimized the fatalities and illustrate the importance of community-based education and awareness programs. The residents of the fishing village Lagunilla were unaware of the tsunami hazard after an earthquake and did not evacuate, which resulted in 3 fatalities. Despite the relatively benign tsunami effects at Pisco from this event, the tsunami hazard for this city (and its liquefied natural gas terminal) cannot be underestimated. Between 1687 and 1868, the city of Pisco was destroyed 4 times by tsunami waves. Since then, two events (1974 and 2007) have resulted in partial inundation and moderate damage. The fact that potentially devastating tsunami runup heights were observed immediately south of the peninsula only serves to underscore this point.

  19. A study of volcanic eruption characteristics using infrasound data recorded on the global IMS network

    NASA Astrophysics Data System (ADS)

    Dabrowa, Amy; Green, David; Phillips, Jeremy; Rust, Alison

    2010-05-01

    Explosive volcanic eruptions have the capability to generate sound waves with infrasonic frequencies (<20Hz). As such waves can propagate over distances of thousands of kilometres within the atmosphere, they present an opportunity to remotely monitor volcanic eruptions and potentially constrain eruptive characteristics. Though most volcanoes in sensitive areas of the world are monitored individually, many volcanoes in remote locations are not monitored directly but can still pose a threat, especially to aviation. The growing International Monitoring System (IMS) network of infrasound stations provides an opportunity to monitor these remote volcanoes. Currently comprising of 43 arrays, the network is designed to achieve global coverage for surface explosions equivalent to a few hundred tonnes of chemical explosive. In recent years work has been published on the detection of specific volcanic eruptions at IMS stations, primarily at regional ranges (< 1000 km from volcano to receiver). In contrast, work presented here looks to create a catalogue of volcanic eruptions that have been detected at IMS stations, with the aim of assessing the capability of the IMS network for use in global volcano monitoring. At this time 40 eruptive events at 19 volcanoes have been investigated from the period 2004 - 2009; however the work is on-going and it is planned to extend this catalogue. In total we document 61 individual detections that have been made on the IMS network. These range from Strombolian activity at Mount Erebus (Antarctica) recorded at a range of 25 km distance, to the Plinian eruption of Manam Volcano (Papua New Guinea) recorded at ranges of over 10,000 km distance. The observed signal frequencies for different eruptions range from less than 0.01 Hz to greater than 5 Hz, and in general, lower frequencies are generated by the larger eruptions. We provide examples of analyses for eruptions recorded at multiple stations (e.g., Manam, October 2004; Kasatochi, August 2008

  20. Infrasound and seismic signals from Baikonur spaceport rocket launches recorded by Kazakh stations

    NASA Astrophysics Data System (ADS)

    Smirnov, Alexandr; Sokolova, Inna; Mikhailova, Natalya

    2015-04-01

    The monitoring network of the Institute of Geophysical Researches, Kazakhstan consists of 2 infrasound arrays, 8 seismic arrays and 7 3C stations. 5 of these stations are a part of IMS CTBTO. The Institute of Geophysical Researches monitors round-the-clock many sorts of seismoacoustic events. Tens of rockets are launched every year from Baikonur spaceport located in Central Kazakhstan. Baikonur rockets fly over several regions of Kazakhstan. Kazakh monitoring stations record launches, rocket stage falls, satellite recovery and sometimes accidents. A catalog of events associated with such activity is built. Some waveform features are collected. The catalog also contains some kinematic and dynamic parameters of the events sources. The signals from accidents of Dnepr rocket of July 26, 2006 and Proton rocket of September 5, 2007 and of July 2, 2013 were studied in details. Discrimination of the events associated with spaceport activity and its exclusion from seismic bulletins allows improving the bulletins quality. And in case of accident this information helps to estimate the event parameters and to start recovery procedures in proper time.

  1. The 2013 Chelyabinsk meteorite: global detection performance of the CTBTO infrasound network

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars; Le Pichon, Alexis; Mialle, Pierrick; Garces, Milton

    2014-05-01

    The explosive fragmentation of the Chelyabinsk meteorite of 15 February 2013 over the Ural Mountains, Russia, generated a large airburst with an equivalent explosive yield of half a megaton of TNT. It is the most energetic event recorded by the infrasound component of the International Monitoring System (IMS) network operated by the Comprehensive Nuclear-Test-Ban Treaty Organization. The event was detected by 20 out of 45 stations of the operational IMS network and propagation paths from the event to the stations ranged between 500 km and 87000 km, traveling more than twice around the globe. The current study in the framework of the ARISE project (http://arise-project.eu/) performs a detailed station-by-station estimation to address why infrasonic signals were clearly detected at some of the stations over very large distances whereas they were not detected at other stations at shorter distances. One potential explanation investigated within this study is the directivity of the signal energy radiated from the meteorite's line source, where azimuth directions at stations perpendicular to the trajectory are favored compared to parallel directions. Another explanation might be different noise and data quality levels at each station, which not only depend on frequency and sensor response, but also on diurnal, seasonal and weather variability. The presentation will provide a station-dependent overview on these parameters compared to the detections of the meteorite event.

  2. The potential of continuous near-field recording of infrasound produced by volcanoes in Vanuatu for probing the the state of the atmosphere.

    NASA Astrophysics Data System (ADS)

    Zielinski, Christelle; Vergniolle, Sylvie; Bani, Philipson; Lardy, Michel; Le Pichon, Alexis; Ponceau, Damien; Gallois, Francis; Herry, Pascal; Todman, Sylvain; Garaebiti, Esline

    2010-05-01

    Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which can be used to monitor the propagation of the waves in the atmosphere, recorded at several hundred of kilometers away. While Lopevi is only producing significant infrasonic waves when an eruptive column of several kilometers high is emplaced in the atmosphere, Marum and Benbow both on Ambrym island and Yasur on Tanna island are permanently generating infrasonic waves. We initially installed, in 2008, an acoustic triangular network on Ambrym volcano to detect strong volcanic explosions, relatively close to the vents, at 2 km. The lack of strong explosions during our 6 months of recordings, with recorded acoustic pressure < 10 Pa, prevented us to use these explosions as natural sources for tracing the propagation path in the atmosphere towards the station IS22 installed at Noumea (New Caledonia), at several hundred of kilometers away. However, the comparison between measurements performed at 2 km with those performed for 3 days at a few hundred of meters from Benbow quantifies the potential of using a triangular acoustic network at a safe distance for monitoring volcanic activity even when very small. Yasur volcano is an outstanding source of infrasonic waves, as its explosions are always sufficiently strong to be recorded at Noumea (New Caledonia). One microbarometer, installed at 300 m from its crater since october 2003, has now recorded several years of activity. The volcanic sound reaches the station IS22 at Noumea during the austral summer, allowing us to compare near-field and far-field signals for a very long period. Our observations in the far-field shows that its volcanic activity is relatively stable, as confirmed by our near-field measurements. We have also performed for a week infrasonic measurements almost directly above the crater to further explore the quality of our continuous measurements in a safe location at a distance of 300 m. In the absence of appropriate

  3. Observer weighting of interaural delays in source and echo clicks.

    PubMed

    Stellmack, M A; Dye, R H; Guzman, S J

    1999-01-01

    A correlational analysis was used to assess the relative weight given to the interaural differences of time (IDTs) of source and echo clicks for echo delays ranging from 1-256 ms. In three different experimental conditions, listeners were instructed to discriminate the IDT of the source, the IDT of the echo, or the difference between the IDTs of the source and echo. The IDT of the target click was chosen randomly and independently from trial-to-trial from a Gaussian distribution (mu = 0 microsecond, sigma = 100 microseconds). The IDT of the nontarget click was either fixed at 0 microsecond or varied in the same manner as the IDT of the target. The data show that for echo delays of 8 ms or less, greater weight was given to the IDT of the source than to that of the echo in all experimental conditions. For echo delays from 16-64 ms, the IDT of the echo was weighted slightly more than that of the source and the weights accounted for a greater proportion of the responses when the echo was the target, indicating that the binaural information in the echo was dominant over the binaural information in the source. The data suggested the possibility that for echo delays from 8-32 ms, listeners were unable to resolve the temporal order of the source and echo IDTs. Listeners were able to weight the binaural information in the source and echo appropriately for a given task only when the echo delay was 128 ms or greater.

  4. Neutron stars as sources of gamma-ray bursts: Constraints from X-ray observations of source locations

    NASA Technical Reports Server (NTRS)

    Pizzichini, G.; Cline, T. L.; Desai, U.; Teegarden, B. J.; Hurley, K.; Niel, M.; Vedrenne, G.; Evans, W. D.; Fenimore, E. E.; Klebesadel, R. W.

    1982-01-01

    Results for three burst locations observed with the imaging proportional counter of the Einstein Observatory are given. The observations are used to determine temperature and accretion constraints for the burst source.

  5. Observations of the rupture development process from source time functions

    NASA Astrophysics Data System (ADS)

    Renou, Julien; Vallée, Martin

    2017-04-01

    The mechanisms governing the seismic rupture expansion and leading to earthquakes of very different magnitudes are still under debate. In the cascade model, the rupture starts from a very small patch, which size is undetectable by seismological investigation. Then rupture grows in a self-similar way, implying that no clues about the earthquake magnitude can be found before rupture starts declining. However dependencies between early phases of the rupture process and final magnitude have also been proposed, which can be explained if an earthquake is more likely to be a big one when its start and early development occur in rupture-prone areas. Here, the analysis of the early phases of the seismic rupture is achieved from an observational point of view using the SCARDEC database, a global catalog containing more than 3000 Source Time Functions (STFs) of earthquakes with magnitude larger than 5.7. This dataset is theoretically very suitable to investigate the initial phase, because STFs directly describe the seismic moment rate released over time, giving access to the rupture growth behavior. As several studies already showed that deep earthquakes tend to have a specific signature of short duration with respect to magnitude (implying a quicker rupture growth than superficial events), only shallow events (depths < 70km) are analyzed here. Our method consists in computing the STFs slope, i.e. the seismic moment acceleration, at several prescribed moment rates. In order to ensure that the chosen moment rates intersect the growth phase of the STF, its value must be high enough to avoid the very beginning of the signal -not well constrained in the deconvolution process-, and low enough to avoid the proximity of the peak moment rate. This approach does not use any rupture time information, which is interesting as (1) the exact hypocentral time can be uncertain and (2) the real rupture expansion can be delayed compared to origin time. If any magnitude-dependent signal exists

  6. 75 FR 37742 - Addition of New Export Control Classification Number 6A981 Passive Infrasound Sensors to the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-30

    ... Classification Number 6A981 Passive Infrasound Sensors to the Commerce Control List of the Export Administration... Control List (CCL) to control passive infrasound sensors because of their military and commercial utility... CONTACT: James Thompson, Sensors and Aviation Division, Bureau of Industry and Security, Telephone: (202...

  7. Infrasound from lightning measured in Ivory Coast from 2004 to 2014

    NASA Astrophysics Data System (ADS)

    Farges, Thomas; Le Pichon, Alexis; Ceranna, Lars; Diawara, Adama

    2016-04-01

    It is well established that more than 2,000 thunderstorms occur continuously around the world and that about 45 lightning flashes are produced per second over the globe. 80 % of the infrasound stations of the International Monitoring System (IMS) of the CTBTO (Comprehensive nuclear Test Ban Treaty Organisation) are now certified and routinely measure signals due to natural activity (e.g., airflow over mountains, aurora, microbaroms, surf, volcanoes, severe weather including lightning flashes …). Some of the IMS stations are located where lightning activity is high (e.g. Africa, South America). These infrasound stations are well localised to study lightning flash activity and its disparity, which is a good proxy for global warming. Progress in infrasound array data processing over the past ten years makes such lightning studies possible. Assink et al. (2008) and Farges and Blanc (2010) show clearly that it is possible to measure lightning infrasound from thunderstorms within 300 km. One-to-one correlation is possible when the thunderstorm is within about 75 km from the station. When the lightning flash occurs within 20 km, it is also possible to rebuild the 3D geometry of the discharges when the network size is less than 100 m (Arechiga et al., 2011; Gallin, 2014). An IMS infrasound station has been installed in Ivory Coast since 2002. The lightning rate of this region is 10-20 flashes/km²/year from space-based instrument OTD (Christian et al., 2003). Ivory Coast is therefore a good place to study infrasound data associated with lightning activity and its temporal variation. First statistical results will be presented in this paper based on 10 years of data (2005-2014). Correlation between infrasound having a mean frequency higher than 1 Hz and lightning flashes detected by the World Wide Lightning Location Network (WWLLN) is systematically looked for. One-to-one correlation is obtained for flashes occurring within about 100 km. An exponential decrease of the

  8. Merging Infrasound and Electromagnetic Signals as a Means for Nuclear Explosion Detection

    NASA Astrophysics Data System (ADS)

    Ashkenazy, Joseph; Lipshtat, Azi; Kesar, Amit S.; Pistinner, Shlomo; Ben Horin, Yochai

    2016-04-01

    The infrasound monitoring network of the CTBT consists of 60 stations. These stations are capable of detecting atmospheric events, and may provide approximate location within time scale of a few hours. However, the nature of these events cannot be deduced from the infrasound signal. More than two decades ago it was proposed to use the electromagnetic pulse (EMP) as a means of discriminating nuclear explosion from other atmospheric events. An EMP is a unique signature of nuclear explosion and is not detected from chemical ones. Nevertheless, it was decided to exclude the EMP technology from the official CTBT verification regime, mainly because of the risk of high false alarm rate, due to lightning electromagnetic pulses [1]. Here we present a method of integrating the information retrieved from the infrasound system with the EMP signal which enables us to discriminate between lightning discharges and nuclear explosions. Furthermore, we show how spectral and other characteristics of the electromagnetic signal emitted from a nuclear explosion are distinguished from those of lightning discharge. We estimate the false alarm probability of detecting a lightning discharge from a given area of the infrasound event, and identifying it as a signature of a nuclear explosion. We show that this probability is very low and conclude that the combination of infrasound monitoring and EMP spectral analysis may produce a reliable method for identifying nuclear explosions. [1] R. Johnson, Unfinished Business: The Negotiation of the CTBT and the End of Nuclear Testing, United Nations Institute for Disarmament Research, 2009.

  9. The influence of periodic wind turbine noise on infrasound array measurements

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars

    2017-02-01

    Aerodynamic noise emissions from the continuously growing number of wind turbines in Germany are creating increasing problems for infrasound recording systems. These systems are equipped with highly sensitive micro pressure sensors accurately measuring acoustic signals in a frequency range inaudible to the human ear. Ten years of data (2006-2015) from the infrasound array IGADE in Northern Germany are analysed to quantify the influence of wind turbine noise on infrasound recordings. Furthermore, a theoretical model is derived and validated by a field experiment with mobile micro-barometer stations. Fieldwork was carried out 2004 to measure the infrasonic pressure level of a single horizontal-axis wind turbine and to extrapolate the sound effect for a larger number of nearby wind turbines. The model estimates the generated sound pressure level of wind turbines and thus enables for specifying the minimum allowable distance between wind turbines and infrasound stations for undisturbed recording. This aspect is particularly important to guarantee the monitoring performance of the German infrasound stations I26DE in the Bavarian Forest and I27DE in Antarctica. These stations are part of the International Monitoring System (IMS) verifying compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), and thus have to meet stringent specifications with respect to infrasonic background noise.

  10. Multiwavelength observations of unidentified high energy gamma ray sources

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1993-01-01

    As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with cataloged objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. Even a rudimentary understanding of their nature awaits identifications and follow-up work at other wavelengths to tell us what they are. The as yet unidentified sources are potentially the most interesting, since they may represent unrecognized new classes of astronomical objects, such as radio-quiet pulsars or new types of active galactic nuclei (AGN's). This two-year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. According to plan, in the first year concentration was on the identification and study of Geminga. The second year will be devoted to studies of similar unidentified gamma-ray sources which will become available in the first EGRET catalogs. The results obtained so far are presented in the two papers which are reproduced in the Appendix. In these papers, we discuss the pulse profiles of Geminga, the geometry and efficiency of the magnetospheric accelerator, the distance to Geminga, the implications for theories of polar cap heating, the effect of the magnetic field on the surface emission and environment of the neutron star, and possible interpretations of a radio-quiet Geminga. The implications of the other gamma-ray pulsars which were discovered to have high gamma-ray efficiency are also discussed, and the remaining unidentified COS B sources are attributed to a population of efficient gamma-ray sources, some of which may be radio quiet.

  11. [Characteristics of infrasound and its influence on workers in working environment of certain thermoelectricity works and department].

    PubMed

    Dang, Wei-Min; Wang, Sheng; Tian, Shi-Xiu; Zhao, Quan-Hong; Chen, Bing; Sun, Fei; He, Li-Hua; Zou, Zhi-Fang; Guo, Zhi-Bin; Ma, Wen-Jun

    2008-12-01

    To study the characteristics of infrasound and its effects on the workers at power plants. The audible noise and infrasound in three thermoelectricity plants were measured and by using Symptom Checklist 90 (SCL-90), the subjective sensation, and the physiological indices were compared between exposed workers and controls. The infrasound levels were different at different measure sites of the three thermoelectricity works ranging from 40 to 98 dB. There was still 40 approximately 80 dB infrasound even when the soot blower stopped running. Different apparatus produced different infrasound levels with the highest ranging from 62 to 115 dB. A single frequency (16 Hz) infrasound was produced in certain department during working hour with sound pressure levels of 110 to 120 dB, but the audible noise sound pressure level was less than 70 dB. There was no significant difference in the indices representing vision fatigue and neurobehaviour function between exposed workers and controls. Workers at certain department experienced evident subjective sensation of neurobehavioral dysfunction, and the scores of somatization, depression, hostility, phobic anxiety, and psychotism in the SCL-90 were significantly higher in the exposed group than in the control and the norm in China (P < 0.05). Infrasound is ubiquitous in the working environment, but usually, the noise levels are less than 120 dB. In some special production department, there is persistent infrasound above 110 to 120 dB. No obvious health effects are found among those who are exposed to infrasound below 100 dB. However, the workers who are chronically exposed to infrasound above 110 to 120 dB present notable subjective sensation of autonomic neurobehavioral dysfunction, and their psychological health status is not as good as those in the control and those in the domestic normal pattern.

  12. Acoustic source characterization of impulsive Strombolian eruptions from the Mount Erebus lava lake

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey; Aster, Richard; Jones, Kyle R.; Kyle, Philip; McIntosh, Bill

    2008-11-01

    We invert for acoustic source volume outflux and momentum imparted to the atmosphere using an infrasonic network distributed about the erupting lava lake at Mount Erebus, Ross Island, Antarctica. By modeling these relatively simple eruptions as monopole point sources we estimate explosively ejected gas volumes that range from 1,000 m 3 to 24,000 m 3 for 312 lava lake eruptions recorded between January 6 and April 13, 2006. Though these volumes are compatible with bubble volumes at rupture (as estimated from explosion video records), departures from isotropic radiation are evident in the recorded acoustic wavefield for many eruptions. A point-source acoustic dipole component with arbitrary axis orientation and strength provides precise fit to the recorded infrasound. This dipole source axis, corresponding to the axis of inferred short-duration material jetting, varies significantly between events. Physical interpretation of dipole orientation as being indicative of eruptive directivity is corroborated by directional emissions of ejecta observed in Erebus eruption video footage. Although three azimuthally distributed stations are insufficient to fully characterize the eruptive acoustic source we speculate that a monopole with a minor amount of oriented dipole radiation may reasonably model the primary features of the recorded infrasound for these eruptions.

  13. Test report for the infrasound prototype: For a CTBT IMS station

    SciTech Connect

    Breding, D.R.; Kromer, R.P.; Whitaker, R.W.; Sandoval, T.

    1997-11-01

    This document describes the results of the Comprehensive Test Ban Treaty (CTBT) Infrasound Prototype Development Test and Evaluation (DT&E). During DT&E the infrasound prototype was evaluated against requirements listed in the System Requirements Document (SRD) based on the Conference on Disarmament/Ad Hoc Committee on a Nuclear Test Ban/Working Papers 224 and 283 and the Preparatory Commission specifications as defined in CTBT/PC/II/1/Add.2, Appendix X, Table 5. The evaluation was conducted during a two-day period, August 6-7, 18997. The System Test Plan (STP) defined the plan and methods to test the infrasound prototype. Specific tests that were performed are detailed in the Test Procedures (TP).

  14. The 2013 Russian fireball largest ever detected by CTBTO infrasound sensors

    NASA Astrophysics Data System (ADS)

    Le Pichon, Alexis; Ceranna, Lars; Pilger, Christoph; Mialle, Pierrick; Brown, David; Herry, Pascal; Brachet, Nicolas

    2013-07-01

    15 February 2013, a large Earth-impacting fireball disintegrated over the Ural Mountains. This extraordinary event is, together with the 1908 Tunguska fireball, among the most energetic events ever instrumentally recorded. It generated infrasound returns, after circling the globe, at distances up to ~85,000 km, and was detected at 20 infrasonic stations of the global International Monitoring System (IMS). For the first time since the establishment of the IMS infrasound network, multiple arrivals involving waves that traveled twice round the globe have been clearly identified. A preliminary estimate of the explosive energy using empirical period-yield scaling relations gives a value of 460 kt of TNT equivalent. In the context of the future verification of the Comprehensive Nuclear-Test-Ban Treaty, this event provides a prominent milestone for studying in detail infrasound propagation around the globe for almost 3 days as well as for calibrating the performance of the IMS network.

  15. The Ionosphere's Pocket Litter: Exploiting Crowd-Sourced Observations

    NASA Astrophysics Data System (ADS)

    Miller, E. S.; Frissell, N. A.; Kaeppler, S. R.; Demajistre, R.; Knuth, A. A.

    2015-12-01

    One of the biggest challenges faced in developing and testing our understanding of the ionosphere is acquiring data that characterizes the latitudinal and longitudinal variability of the ionosphere. While there are extensive networks of ground sites that sample the vertical distribution, we have rather poor coverage over the oceans and in parts of the southern hemisphere. Our ability to validate the ionospheric models is limited by the lack of point measurements and those measurements that essentially constitute characterization of horizontal gradients. In this talk, we discuss and demonstrate the use of various types of crowd-sourced information that enables us to extend our coverage over these regions. We will discuss new sources of these data, concepts for new experiments and the use of these data in assimilative models. We note that there are new, low cost options for obtaining data that broaden the participation beyond the aeronomy/ionospheric community.

  16. Design of infrasound-detection system via adaptive LMSTDE algorithm

    NASA Technical Reports Server (NTRS)

    Khalaf, C. S.; Stoughton, J. W.

    1984-01-01

    A proposed solution to an aviation safety problem is based on passive detection of turbulent weather phenomena through their infrasonic emission. This thesis describes a system design that is adequate for detection and bearing evaluation of infrasounds. An array of four sensors, with the appropriate hardware, is used for the detection part. Bearing evaluation is based on estimates of time delays between sensor outputs. The generalized cross correlation (GCC), as the conventional time-delay estimation (TDE) method, is first reviewed. An adaptive TDE approach, using the least mean square (LMS) algorithm, is then discussed. A comparison between the two techniques is made and the advantages of the adaptive approach are listed. The behavior of the GCC, as a Roth processor, is examined for the anticipated signals. It is shown that the Roth processor has the desired effect of sharpening the peak of the correlation function. It is also shown that the LMSTDE technique is an equivalent implementation of the Roth processor in the time domain. A LMSTDE lead-lag model, with a variable stability coefficient and a convergence criterion, is designed.

  17. Effect of interarray elevation differences on infrasound beamforming

    NASA Astrophysics Data System (ADS)

    Edwards, Wayne N.; Green, David N.

    2012-07-01

    The International Monitoring System infrasound network will, upon completion, contain 60 microbarometer arrays with apertures of between 1 and 4 km. These arrays are located within a variety of terrains, leading to large ratios of interelement elevation differences to array aperture for those arrays situated in areas of significant topography. Systematic errors in beamforming estimates caused by neglecting the vertical extent of the arrays, are quantified for both signal backazimuth and apparent velocity. Of the 43 arrays certified as of 2011 January, I14CL on Juan Fernandez Island has the greatest topography across an array, with a least-squares fitted plane through the array elements having an 8.1° slope from the horizontal (compared to a network mean of 1.6°). Beamforming errors (both backazimuth and apparent velocity) are a function of the arrival azimuth and become increasingly large for steeply inclined arrivals, such that systematic errors will be significantly larger for signals returned from the thermosphere compared to those from the stratosphere. At several arrays, azimuthal errors due to array topography are comparable in magnitude to deviations often associated with atmospheric propagation. These findings are illustrated using signals recorded in Greenland at I18DK, where differences between results processed using both full 3-D array geometry and the 2-D (topography neglected) approximation exhibit good correspondence to theoretical predictions.

  18. Implementation and evaluation of an inexpensive low-power low-noise infrasound sensor and its use in a dense sensor network around an active volcanic vent

    NASA Astrophysics Data System (ADS)

    Marcillo, O. E.; Johnson, J. B.; Hart, D. M.

    2011-12-01

    The development and evaluation of a low-cost infrasound sensor, the infraNMT, and its use as part of a dense (45-element) sensor network around an active volcanic vent, are described. This sensor is based on a commercial micro-machined piezo-resistive differential pressure transducer that uses a mechanical high-pass filter to reject low-frequency out-band energy. The sensor features low noise, 2.02 mPa rms (0.5-2 Hz), 5.47 mPa RMS (0.1-20 Hz), or 5.62 mPa rms (0.05-20 Hz), flat response between 0.01 Hz to at least 40 Hz, inband sensitivity of 45.13 +/-0.23 μV/Pa, and nominal linear range of -124.5 to +124.5 Pa. The sensor consumes a minimum of 24 mW, and operates with voltages above 8V while drawing 3mA of current. The infraNMT specifications described above were independently verified using the infrasound test chamber at the Sandia National Laboratories' Facility for Acceptance, Calibration, and Testing (SNL-FACT) and following procedures for comparison calibration against traceable reference stands in voltage and pressure. Due to the intended broad frequency response of this sensor the testing chamber was configured in a double reference sensor scheme. A well-characterized MB2000 micro-barometer (with a flat amplitude response between 0.01 and 8 Hz) and microphone (with a flat amplitude response above 8Hz) were used simultaneously in this double reference test configuration. The characteristics of the infraNMT, including small size, low power consumption, high dynamic range, and low cost, favor its use in array or network configurations for near source and/or higher noise environments. This sensor has been used for infrasound array studies associated with various sources, including volcanic and chemical explosions, glacier earthquakes, and thunder. In this study we report on the Summer 2010 deployment of a network of 45 infraNMT sensors at Kilauea volcano to study the infrasound generated by degassing of the active Halema'uma'u vent. For this experiment, the

  19. Dynamics of the Bingham Canyon rock avalanches (Utah, USA) resolved from topographic, seismic, and infrasound data: Bingham Canyon Rock Avalanches

    DOE PAGES

    Moore, Jeffrey R.; Pankow, Kristine L.; Ford, Sean R.; ...

    2017-03-01

    The 2013 Bingham Canyon Mine rock avalanches represent one of the largest cumulative landslide events in recorded U.S. history and provide a unique opportunity to test remote analysis techniques for landslide characterization. We combine aerial photogrammetry surveying, topographic reconstruction, numerical runout modeling, and analysis of broadband seismic and infrasound data to extract salient details of the dynamics and evolution of the multiphase landslide event. Our results reveal a cumulative intact rock source volume of 52 Mm3, which mobilized in two main rock avalanche phases separated by 1.5 h. We estimate that the first rock avalanche had 1.5–2 times greater volumemore » than the second. Each failure initiated by sliding along a gently dipping (21°), highly persistent basal fault before transitioning to a rock avalanche and spilling into the inner pit. The trajectory and duration of the two rock avalanches were reconstructed using runout modeling and independent force history inversion of intermediate-period (10–50 s) seismic data. Intermediate- and shorter-period (1–50 s) seismic data were sensitive to intervals of mass redirection and constrained finer details of the individual slide dynamics. Back projecting short-period (0.2–1 s) seismic energy, we located the two rock avalanches within 2 and 4 km of the mine. Further analysis of infrasound and seismic data revealed that the cumulative event included an additional 11 smaller landslides (volumes ~104–105 m3) and that a trailing signal following the second rock avalanche may result from an air-coupled Rayleigh wave. These results demonstrate new and refined techniques for detailed remote characterization of the dynamics and evolution of large landslides.« less

  20. Determining the Intensity of a Point-Like Source Observed on the Background of AN Extended Source

    NASA Astrophysics Data System (ADS)

    Kornienko, Y. V.; Skuratovskiy, S. I.

    2014-12-01

    The problem of determining the time dependence of intensity of a point-like source in case of atmospheric blur is formulated and solved by using the Bayesian statistical approach. A pointlike source is supposed to be observed on the background of an extended source with constant in time though unknown brightness. The equation system for optimal statistical estimation of the sequence of intensity values in observation moments is obtained. The problem is particularly relevant for studying gravitational mirages which appear while observing a quasar through the gravitational field of a far galaxy.

  1. Tropical sources and sinks of carbonyl sulfide observed from space

    NASA Astrophysics Data System (ADS)

    Glatthor, N.; Höpfner, M.; Baker, I. T.; Berry, J.; Campbell, J. E.; Kawa, S. R.; Krysztofiak, G.; Leyser, A.; Sinnhuber, B.-M.; Stiller, G. P.; Stinecipher, J.; Clarmann, T.

    2015-11-01

    According to current budget estimations the seasonal variation of carbonyl sulfide (COS) is governed by oceanic release and vegetation uptake. Its assimilation by plants is assumed to be similar to the photosynthetic uptake of CO2 but, contrary to the latter process, to be irreversible. Therefore, COS has been suggested as cotracer of the carbon cycle. Observations of COS, however, are sparse, especially in tropical regions. We use the comprehensive data set of spaceborne measurements of the Michelson Interferometer for Passive Atmospheric Sounding to analyze its global distribution. Two major features are observed in the tropical upper troposphere around 250 hPa: enhanced amounts over the western Pacific and the Maritime Continent, peaking around 550 parts per trillion by volume (pptv) in boreal summer, and a seasonally varying depletion of COS extending from tropical South America to Africa. The large-scale COS depletion, which in austral summer amounts up to -40 pptv as compared to the rest of the respective latitude band, has not been observed before and reveals the seasonality of COS uptake through tropical vegetation. The observations can only be reproduced by global models, when a large vegetation uptake and a corresponding increase in oceanic emissions as proposed in several recent publications are assumed.

  2. Tropical sources and sinks of carbonyl sulfide observed from space

    NASA Astrophysics Data System (ADS)

    Glatthor, Norbert; Höpfner, Michael; Baker, Ian T.; Berry, Joe; Campbell, Elliott; Kawa, Stephan R.; Krysztofiak, Gisele; Sinnhuber, Björn-Martin; Stiller, Gabriele; Stinecipher, Jim; von Clarmann, Thomas

    2016-04-01

    According to current budget estimations the seasonal variation of carbonyl sulfide (COS) is governed by oceanic release and vegetation uptake. Its assimilation by plants is assumed to be similar to the photosynthetic uptake of CO2 but, contrary to the latter process, to be irreversible. Therefore COS has been suggested as co-tracer of the carbon cycle. Observations of COS, however, are sparse, especially in tropical regions. We use the comprehensive data set of spaceborne measurements of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) to analyze its global distribution. Two major features are observed in the tropical upper troposphere around 250 hPa: enhanced amounts over the western Pacific and the Maritime Continent, peaking around 550 pptv in boreal summer, and a seasonally varying depletion of COS extending from tropical South America to Africa. The large-scale COS depletion, which in austral summer amounts up to -40 pptv as compared to the rest of the respective latitude band, has not been observed before and reveals the seasonality of COS uptake through tropical vegetation. The observations can only be reproduced by global models, when a large vegetation uptake and a corresponding increase in oceanic emissions as proposed in several recent publications is assumed.

  3. Observations of collective effects at the Advanced Light Source

    SciTech Connect

    Byrd, J.M.; Barry, W.; Corlett, J.N.; Fox, J.; Teytelman, D.

    1995-10-01

    We present a summary of measurements of single beam collective effects in the Advanced Light Source (ALS). We describe measurements of coupled-bunch instabilities, including some recent results using the newly commissioned feedback systems and the results of an initial search for the fast ion instability. Single bunch effects include bunch lengthening, energy spread increase, HOM loss measurements, head-tail damping rates, current dependent tune shifts, and transverse mode coupling instability threshold. The longitudinal measurements are consistent with a broadband impedance {vert_bar}{Zeta}{sub {parallel}}/{eta}{vert_bar}{sub eff} = 0.22{plus_minus}0.07 {Omega} and transverse measurements indicate broadband impedances of {Zeta}{sub y,eff} = 155 k{Omega}/m and Z{sub x,eff} = 58 k{Omega}/m.

  4. Testing nonlocal observation as a source of intuitive knowledge.

    PubMed

    Radin, Dean

    2008-01-01

    This study explored the hypothesis that in some cases intuitive knowledge arises from perceptions that are not mediated through the ordinary senses. The possibility of detecting such nonlocal observation was investigated in a pilot test based on the effects of observation on a quantum system. Participants were asked to imagine that they could intuitively perceive a low-intensity laser beam in a distant Michelson interferometer. If such observation were possible, it would theoretically perturb the photons' quantum wave functions and change the pattern of light produced by the interferometer. The optical apparatus was located inside a light-tight, double-steel walled, shielded chamber. Participants sat quietly outside the chamber with eyes closed. The light patterns were recorded by a cooled digital camera once per second, and average illumination levels of these images were compared in counterbalanced mental blocking versus nonblocking conditions. By design, perturbation would produce a lower overall level of illumination, which was predicted to occur during the blocking condition. Based on a series of planned experimental sessions, the outcome was in accordance with the prediction (z = -2.82; P = .002). This result was primarily due to nine sessions involving experienced meditators (combined z = -4.28; P = 9.4 x 10(-6)); the other nine sessions with nonmeditators were not significant (combined z = 0.29; P = .61). The same experimental protocol run immediately after 15 of these test sessions, but with no one present, revealed no hardware or protocol artifacts that might have accounted for these results (combined control z = 1.50; P = .93). Conventional explanations for these results were considered and judged to be implausible. This pilot study suggests the presence of a nonlocal perturbation effect that is consistent with traditional concepts of intuition as a direct means of gaining knowledge about the world, and with the predicted effects of observation on a

  5. Observation of Neutron Skyshine from an Accelerator Based Neutron Source

    NASA Astrophysics Data System (ADS)

    Franklyn, C. B.

    2011-12-01

    A key feature of neutron based interrogation systems is the need for adequate provision of shielding around the facility. Accelerator facilities adapted for fast neutron generation are not necessarily suitably equipped to ensure complete containment of the vast quantity of neutrons generated, typically >1011 nṡs-1. Simulating the neutron leakage from a facility is not a simple exercise since the energy and directional distribution can only be approximated. Although adequate horizontal, planar shielding provision is made for a neutron generator facility, it is sometimes the case that vertical shielding is minimized, due to structural and economic constraints. It is further justified by assuming the atmosphere above a facility functions as an adequate radiation shield. It has become apparent that multiple neutron scattering within the atmosphere can result in a measurable dose of neutrons reaching ground level some distance from a facility, an effect commonly known as skyshine. This paper describes a neutron detection system developed to monitor neutrons detected several hundred metres from a neutron source due to the effect of skyshine.

  6. Riverine source of Arctic Ocean mercury inferred from atmospheric observations

    NASA Astrophysics Data System (ADS)

    Fisher, Jenny A.; Jacob, Daniel J.; Soerensen, Anne L.; Amos, Helen M.; Steffen, Alexandra; Sunderland, Elsie M.

    2012-07-01

    Methylmercury is a potent neurotoxin that accumulates in aquatic food webs. Human activities, including industry and mining, have increased inorganic mercury inputs to terrestrial and aquatic ecosystems. Methylation of this mercury generates methylmercury, and is thus a public health concern. Marine methylmercury is a particular concern in the Arctic, where indigenous peoples rely heavily on marine-based diets. In the summer, atmospheric inorganic mercury concentrations peak in the Arctic, whereas they reach a minimum in the northern mid-latitudes. Here, we use a global three-dimensional ocean-atmosphere model to examine the cause of this Arctic summertime maximum. According to our simulations, circumpolar rivers deliver large quantities of mercury to the Arctic Ocean during summer; the subsequent evasion of this riverine mercury to the atmosphere can explain the summertime peak in atmospheric mercury levels. We infer that rivers are the dominant source of mercury to the Arctic Ocean on an annual basis. Our simulations suggest that Arctic Ocean mercury concentrations could be highly sensitive to climate-induced changes in river flow, and to increases in the mobility of mercury in soils, for example as a result of permafrost thaw and forest fires.

  7. Possibility of observable signatures of leptonium from astrophysical sources

    NASA Astrophysics Data System (ADS)

    Ellis, S. C.; Bland-Hawthorn, Joss

    2015-06-01

    The formation of positronium in our Galaxy is well measured, and has led to important and unanswered questions on the origin of the positrons. In principle it should be possible to form analogous systems from μ and τ leptons, viz. true muonium and true tauonium. However the probability of formation for these systems is greatly reduced due to the intrinsically short lifetimes of the μ and τ leptons. Likewise, the decay of the atoms is hastened by the high probability of the constituent particles decaying. Nevertheless, if sufficient numbers of μ and τ pairs are produced in high energy astrophysical environments there may be significant production of true muonium and true tauonium, despite the small probabilities. This paper addresses this possibility. We have calculated the pair production spectra of μ and τ leptons from photon-photon annihilation and electron-positron annihilation in astrophysical environments. We have computed the cross sections for radiative recombination and direct annihilation of the pairs, and the decay constants for the various allowable decays, and the wavelengths and energies of the recombination and annihilation signatures. In this way we have calculated the probabilities for the formation of true muonium and true tauonium, and the branching ratios for the various observable signatures. We have estimated the expected fluxes from accretion disks around microquasars and active galactic nuclei, and from interactions of jets with clouds and stars. We find that accretion disks around stellar mass black holes in our own Galaxy should have observable signatures at x-ray and γ -ray energies that are in principle observable with current observatories.

  8. Seasonal variations of infrasonic arrivals from long term ground truth observations in Nevada and implication for event location

    NASA Astrophysics Data System (ADS)

    Negraru, Petru; Golden, Paul

    2017-01-01

    SUMMARYLong term ground truth <span class="hlt">observations</span> were collected at two <span class="hlt">infrasound</span> arrays in Nevada to investigate how seasonal atmospheric variations affect the detection, travel time and signal characteristics (azimuth, trace velocity, frequency content and amplitudes) of infrasonic arrivals at regional distances. The arrays were located in different azimuthal directions from a munition disposal facility in Nevada. FNIAR, located 154 km north of the <span class="hlt">source</span> has a high detection rate throughout the year. Over 90% of the detonations have travel times indicative of stratospheric arrivals, while tropospheric waveguides are <span class="hlt">observed</span> from only 27% of the detonations. The second array, DNIAR, located 293 km southeast of the <span class="hlt">source</span> exhibits strong seasonal variations with high stratospheric detection rates in winter and the virtual absence of stratospheric arrivals in summer. Tropospheric waveguides and thermospheric arrivals are also <span class="hlt">observed</span> for DNIAR. Modelling through the Naval Research Laboratory Ground to Space (G2S) atmospheric sound speeds leads to mixed results: FNIAR arrivals are usually not predicted to be present at all (either stratospheric or tropospheric), while DNIAR arrivals are usually correctly predicted, but summer arrivals show a consistent travel time bias. In the end we show the possible improvement in location using empirically calibrated travel time and azimuth <span class="hlt">observations</span>. Using the Bayesian <span class="hlt">Infrasound</span> <span class="hlt">Source</span> Localization we show that we can decrease the area enclosed by the 90% credibility contours by a factor of 2.5.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoJI.209..373N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoJI.209..373N"><span>Seasonal variations of infrasonic arrivals from long-term ground truth <span class="hlt">observations</span> in Nevada and implication for event location</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Negraru, Petru; Golden, Paul</p> <p>2017-04-01</p> <p>Long-term ground truth <span class="hlt">observations</span> were collected at two <span class="hlt">infrasound</span> arrays in Nevada to investigate how seasonal atmospheric variations affect the detection, traveltime and signal characteristics (azimuth, trace velocity, frequency content and amplitudes) of infrasonic arrivals at regional distances. The arrays were located in different azimuthal directions from a munition disposal facility in Nevada. FNIAR, located 154 km north of the <span class="hlt">source</span> has a high detection rate throughout the year. Over 90 per cent of the detonations have traveltimes indicative of stratospheric arrivals, while tropospheric waveguides are <span class="hlt">observed</span> from only 27 per cent of the detonations. The second array, DNIAR, located 293 km southeast of the <span class="hlt">source</span> exhibits strong seasonal variations with high stratospheric detection rates in winter and the virtual absence of stratospheric arrivals in summer. Tropospheric waveguides and thermospheric arrivals are also <span class="hlt">observed</span> for DNIAR. Modeling through the Naval Research Laboratory Ground to Space atmospheric sound speeds leads to mixed results: FNIAR arrivals are usually not predicted to be present at all (either stratospheric or tropospheric), while DNIAR arrivals are usually correctly predicted, but summer arrivals show a consistent traveltime bias. In the end, we show the possible improvement in location using empirically calibrated traveltime and azimuth <span class="hlt">observations</span>. Using the Bayesian <span class="hlt">Infrasound</span> <span class="hlt">Source</span> Localization we show that we can decrease the area enclosed by the 90 per cent credibility contours by a factor of 2.5.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..APR.M9003I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..APR.M9003I"><span><span class="hlt">Observing</span> the Earliest Galaxies: Looking for the <span class="hlt">Sources</span> of Reionization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Illingworth, Garth</p> <p>2015-04-01</p> <p>Systematic searches for the earliest galaxies in the reionization epoch finally became possible in 2009 when the Hubble Space Telescope was updated with a powerful new infrared camera during the final Shuttle servicing mission SM4 to Hubble. The reionization epoch represents the last major phase transition of the universe and was a major event in cosmic history. The intense ultraviolet radiation from young star-forming galaxies is increasingly considered to be the <span class="hlt">source</span> of the photons that reionized intergalactic hydrogen in the period between the ``dark ages'' (the time before the first stars and galaxies at about 100-200 million years after the Big Bang) and the end of reionization around 800-900 million years. Yet finding and measuring the earliest galaxies in this era of cosmic dawn has proven to a challenging task, even with Hubble's new infrared camera. I will discuss the deep imaging undertaken by Hubble and the remarkable insights that have accrued from the imaging datasets taken over the last decade on the Hubble Ultra-Deep Field (HUDF, HUDF09/12) and other regions. The HUDF datasets are central to the story and have been assembled into the eXtreme Deep Field (XDF), the deepest image ever from Hubble data. The XDF, when combined with results from shallower wide-area imaging surveys (e.g., GOODS, CANDELS) and with detections of galaxies from the Frontier Fields, has provided significant insights into the role of galaxies in reionization. Yet many questions remain. The puzzle is far from being fully solved and, while much will done over the next few years, the solution likely awaits the launch of JWST. NASA/STScI Grant HST-GO-11563.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMIN21C3715F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMIN21C3715F"><span>Open <span class="hlt">Source</span> Dataturbine (OSDT) Android Sensorpod in Environmental <span class="hlt">Observing</span> Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fountain, T. R.; Shin, P.; Tilak, S.; Trinh, T.; Smith, J.; Kram, S.</p> <p>2014-12-01</p> <p>The OSDT Android SensorPod is a custom-designed mobile computing platform for assembling wireless sensor networks for environmental monitoring applications. Funded by an award from the Gordon and Betty Moore Foundation, the OSDT SensorPod represents a significant technological advance in the application of mobile and cloud computing technologies to near-real-time applications in environmental science, natural resources management, and disaster response and recovery. It provides a modular architecture based on open standards and open-<span class="hlt">source</span> software that allows system developers to align their projects with industry best practices and technology trends, while avoiding commercial vendor lock-in to expensive proprietary software and hardware systems. The integration of mobile and cloud-computing infrastructure represents a disruptive technology in the field of environmental science, since basic assumptions about technology requirements are now open to revision, e.g., the roles of special purpose data loggers and dedicated site infrastructure. The OSDT Android SensorPod was designed with these considerations in mind, and the resulting system exhibits the following characteristics - it is flexible, efficient and robust. The system was developed and tested in the three science applications: 1) a fresh water limnology deployment in Wisconsin, 2) a near coastal marine science deployment at the UCSD Scripps Pier, and 3) a terrestrial ecological deployment in the mountains of Taiwan. As part of a public education and outreach effort, a Facebook page with daily ocean pH measurements from the UCSD Scripps pier was developed. Wireless sensor networks and the virtualization of data and network services is the future of environmental science infrastructure. The OSDT Android SensorPod was designed and developed to harness these new technology developments for environmental monitoring applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21313636','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21313636"><span>MILAGRO <span class="hlt">OBSERVATIONS</span> OF MULTI-TeV EMISSION FROM GALACTIC <span class="hlt">SOURCES</span> IN THE FERMI BRIGHT <span class="hlt">SOURCE</span> LIST</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Abdo, A. A.; Linnemann, J. T.; Allen, B. T.; Chen, C.; Aune, T.; Berley, D.; Goodman, J. A.; Christopher, G. E.; Kolterman, B. E.; Mincer, A. I.; Nemethy, P.; DeYoung, T.; Dingus, B. L.; Hoffman, C. M.; Ellsworth, R. W.; Gonzalez, M. M.; Hays, E.; McEnery, J. E.; Huentemeyer, P. H.; Morgan, T.</p> <p>2009-08-01</p> <p>We present the result of a search of the Milagro sky map for spatial correlations with <span class="hlt">sources</span> from a subset of the recent Fermi Bright <span class="hlt">Source</span> List (BSL). The BSL consists of the 205 most significant <span class="hlt">sources</span> detected above 100 MeV by the Fermi Large Area Telescope. We select <span class="hlt">sources</span> based on their categorization in the BSL, taking all confirmed or possible Galactic <span class="hlt">sources</span> in the field of view of Milagro. Of the 34 Fermi <span class="hlt">sources</span> selected, 14 are <span class="hlt">observed</span> by Milagro at a significance of 3 standard deviations or more. We conduct this search with a new analysis which employs newly optimized gamma-hadron separation and utilizes the full eight-year Milagro data set. Milagro is sensitive to gamma rays with energy from 1 to 100 TeV with a peak sensitivity from 10 to 50 TeV depending on the <span class="hlt">source</span> spectrum and declination. These results extend the <span class="hlt">observation</span> of these <span class="hlt">sources</span> far above the Fermi energy band. With the new analysis and additional data, multi-TeV emission is definitively <span class="hlt">observed</span> associated with the Fermi pulsar, J2229.0+6114, in the Boomerang pulsar wind nebula (PWN). Furthermore, an extended region of multi-TeV emission is associated with the Fermi pulsar, J0634.0+1745, the Geminga pulsar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820040381&hterms=ISIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DISIS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820040381&hterms=ISIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DISIS"><span>Auroral kilometric radiation <span class="hlt">source</span> region <span class="hlt">observations</span> from ISIS 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Benson, R. F.</p> <p>1981-01-01</p> <p>The ISIS 1 <span class="hlt">observations</span> of the high-frequency portion of the auroral kilometric radiation (AKR) spectrum are considered, that is, from the minimum frequency encountered for the extraordinary mode cut-off (approximately 450 kHz) to the upper frequency cut-off (approximately 800 kHz). AKR is found to be generated in the extraordinary mode just above the local cutoff frequency and to emanate in a direction that is nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is below 0.2. The density depletion is restricted to altitudes above approximately 2,000 km, and the upper AKR frequency limit corresponds to the extraordinary cutoff frequency at this altitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820040381&hterms=Isis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DIsis','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820040381&hterms=Isis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DIsis"><span>Auroral kilometric radiation <span class="hlt">source</span> region <span class="hlt">observations</span> from ISIS 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Benson, R. F.</p> <p>1981-01-01</p> <p>The ISIS 1 <span class="hlt">observations</span> of the high-frequency portion of the auroral kilometric radiation (AKR) spectrum are considered, that is, from the minimum frequency encountered for the extraordinary mode cut-off (approximately 450 kHz) to the upper frequency cut-off (approximately 800 kHz). AKR is found to be generated in the extraordinary mode just above the local cutoff frequency and to emanate in a direction that is nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is below 0.2. The density depletion is restricted to altitudes above approximately 2,000 km, and the upper AKR frequency limit corresponds to the extraordinary cutoff frequency at this altitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...847L..20V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...847L..20V"><span>AGILE <span class="hlt">Observations</span> of the Gravitational-wave <span class="hlt">Source</span> GW170104</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Verrecchia, F.; Tavani, M.; Ursi, A.; Argan, A.; Pittori, C.; Donnarumma, I.; Bulgarelli, A.; Fuschino, F.; Labanti, C.; Marisaldi, M.; Evangelista, Y.; Minervini, G.; Giuliani, A.; Cardillo, M.; Longo, F.; Lucarelli, F.; Munar-Adrover, P.; Piano, G.; Pilia, M.; Fioretti, V.; Parmiggiani, N.; Trois, A.; Del Monte, E.; Antonelli, L. A.; Barbiellini, G.; Caraveo, P.; Cattaneo, P. W.; Colafrancesco, S.; Costa, E.; D’Amico, F.; Feroci, M.; Ferrari, A.; Morselli, A.; Pacciani, L.; Paoletti, F.; Pellizzoni, A.; Picozza, P.; Rappoldi, A.; Vercellone, S.</p> <p>2017-10-01</p> <p>The LIGO/Virgo Collaboration (LVC) detected on 2017 January 4 a significant gravitational-wave (GW) event (now named GW170104). We report in this Letter the main results obtained from the analysis of hard X-ray and gamma-ray data of the AGILE mission that repeatedly <span class="hlt">observed</span> the GW170104 localization region (LR). At the LVC detection time T 0 AGILE <span class="hlt">observed</span> about 36% of the LR. The gamma-ray imaging detector did not reveal any significant emission in the energy range 50 MeV–30 GeV. Furthermore, no significant gamma-ray transients were detected in the LR that was repeatedly exposed over timescales of minutes, hours, and days. We also searched for transient emission using data near T 0 of the omnidirectional detector MCAL operating in the energy band 0.4–100 MeV. A refined analysis of MCAL data shows the existence of a weak event (that we call “E2”) with a signal-to-noise ratio of 4.4σ lasting about 32 ms and occurring 0.46 ± 0.05 s before T 0. A study of the MCAL background and of the false-alarm rate of E2 leads to the determination of a post-trial significance between 2.4σ and 2.7σ for a temporal coincidence with GW170104. We note that E2 has characteristics similar to those detected from the weak precursor of GRB 090510. The candidate event E2 is worth consideration for simultaneous detection by other satellites. If associated with GW170104, it shows emission in the MeV band of a short burst preceding the final coalescence by 0.46 s and involving ∼10‑7 of the total rest mass energy of the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840018452','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840018452"><span>Catalog of infrared <span class="hlt">observations</span> including: Bibliography of infrared astronomy and index of infrared <span class="hlt">source</span> positions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gezari, D. Y.; Schmitz, M.; Mead, J. M.</p> <p>1984-01-01</p> <p>The Catalog of Infrared <span class="hlt">Observations</span> and its Far Infrared Supplement summarize all infrared astronomical <span class="hlt">observations</span> at infrared wavelengths published in the scientific literature between 1965 and 1982. The Catalog includes as appendices the Bibliography of infrared astronomy which keys <span class="hlt">observations</span> in the Catalog with the original journal references, and the index of infrared <span class="hlt">source</span> positions which gives <span class="hlt">source</span> positions for alphabetically listed <span class="hlt">sources</span> in the Catalog. The Catalog data base contains over 85,000 <span class="hlt">observations</span> of about 10,000 infrared <span class="hlt">sources</span>, of which about 2,000 have no known visible counterpart.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993GMS....80..239M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993GMS....80..239M"><span>DE 1 particle and wave <span class="hlt">observations</span> in an AKR <span class="hlt">source</span> region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menietti, J. D.; Burch, J. L.</p> <p></p> <p>Near the AKR <span class="hlt">source</span> region wave-particle interactions appear to have modified the <span class="hlt">observed</span> electron distributions. We compare the <span class="hlt">observations</span> to those predicted by recently published numerical simulations. <span class="hlt">Observations</span> of electron distributions indicate a region of perpendicular heating (T⊥/T∥>10) adjacent to and within the <span class="hlt">source</span> region. Loss cones, trapped particles, beams, and electron conical distributions are also <span class="hlt">observed</span> near and within the <span class="hlt">source</span> region, which extends perpendicular to the magnetic field line for at least 20 km in a density cavity. The high altitude plasma instrument on board the DE 1 satellite was operating during a near crossing of the AKR <span class="hlt">source</span> in the nightside auroral region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993JGR....98.5865M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993JGR....98.5865M"><span>DE 1 particle and wave <span class="hlt">observations</span> in Auroral Kilometric Radiation (AKR) <span class="hlt">source</span> regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menietti, J. D.; Burch, J. L.; Winglee, R. M.; Gurnett, D. A.</p> <p>1993-04-01</p> <p>The high-altitude plasma instrument on board the DE 1 satellite was operating during several near crossings of the AKR <span class="hlt">source</span> in the nightside auroral region. <span class="hlt">Observations</span> of electron distributions indicate a region of perpendicular heating adjacent to, and within, the <span class="hlt">source</span> region. Loss cones, trapped particles, beams, and electron conical distributions are also <span class="hlt">observed</span> near and within the <span class="hlt">source</span> region, which extends perpendicular to the magnetic field line for at least 20 km. Near the AKR <span class="hlt">source</span> region wave-particle interactions appear to have modified the <span class="hlt">observed</span> electron distributions. We compare the <span class="hlt">observations</span> to those predicted by recently published numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/986599','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/986599"><span><span class="hlt">Observations</span> on vapor pressure in SPR caverns : <span class="hlt">sources</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Munson, Darrell Eugene</p> <p>2010-05-01</p> <p>The oil of the Strategic Petroleum Reserve (SPR) represents a national response to any potential emergency or intentional restriction of crude oil supply to this country, and conforms to International Agreements to maintain such a reserve. As assurance this reserve oil will be available in a timely manner should a restriction in supply occur, the oil of the reserve must meet certain transportation criteria. The transportation criteria require that the oil does not evolve dangerous gas, either explosive or toxic, while in the process of transport to, or storage at, the destination facility. This requirement can be a challenge because the stored oil can acquire dissolved gases while in the SPR. There have been a series of reports analyzing in exceptional detail the reasons for the increases, or regains, in gas content; however, there remains some uncertainty in these explanations and an inability to predict why the regains occur. Where the regains are prohibitive and exceed the criteria, the oil must undergo degasification, where excess portions of the volatile gas are removed. There are only two known <span class="hlt">sources</span> of gas regain, one is the salt dome formation itself which may contain gas inclusions from which gas can be released during oil processing or storage, and the second is increases of the gases release by the volatile components of the crude oil itself during storage, especially if the stored oil undergoes heating or is subject to biological generation processes. In this work, the earlier analyses are reexamined and significant alterations in conclusions are proposed. The alterations are based on how the fluid exchanges of brine and oil uptake gas released from domal salt during solutioning, and thereafter, during further exchanges of fluids. Transparency of the brine/oil interface and the transfer of gas across this interface remains an important unanswered question. The contribution from creep induced damage releasing gas from the salt surrounding the cavern is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/6472092','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/6472092"><span>[Flow of high-voltage current in coal electrodes of arc furnaces as a <span class="hlt">source</span> of noise of special nature].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Polanowska, R</p> <p>1984-01-01</p> <p>The noise level for working arc furnace has been measured. Arc furnaces were found to be the <span class="hlt">source</span> of <span class="hlt">infrasounds</span> and acoustic field. The sound pressure levels for <span class="hlt">infrasounds</span> range from 55 to 77 dB. It has been showed that particular noise level includes the onethird-octave band with middle frequency 100 Hz. The sound pressure levels in this band range from 105 to 110 dB.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EP%26S...68...24C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EP%26S...68...24C"><span>Ionospheric signatures of the April 25, 2015 Nepal earthquake and the relative role of compression and advection for Doppler sounding of <span class="hlt">infrasound</span> in the ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chum, Jaroslav; Liu, Jann-Yenq; Laštovička, Jan; Fišer, Jiří; Mošna, Zbyšek; Baše, Jiří; Sun, Yang-Yi</p> <p>2016-02-01</p> <p>Ionospheric signatures possibly induced by the Nepal earthquake are investigated far outside the epicentral region in Taiwan (~3700 km distance from the epicenter) and in the Czech Republic (~6300 km distance from the epicenter). It is shown that the ionospheric disturbances were caused by long period, ~20 s, <span class="hlt">infrasound</span> waves that were excited locally by vertical component of the ground surface motion and propagated nearly vertically to the ionosphere. The <span class="hlt">infrasound</span> waves are heavily damped at the heights of F layer at around 200 km, so their amplitude strongly depends on the altitude of <span class="hlt">observation</span>. In addition, in the case of continuous Doppler sounding, the value of the Doppler shift depends not only on the advection (up and down motion) of the reflecting layer but also on the compression/rarefaction of the electron gas and hence on the electron density gradient. Consequently, under significant differences of reflection height of sounding radio waves and partly also under large differences in plasma density gradients, the <span class="hlt">observed</span> ionospheric response at larger distances from the epicenter can be comparable with the ionospheric response <span class="hlt">observed</span> at shorter distances, although the amplitudes of causative seismic motions differ by more than one order of magnitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3656933','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3656933"><span>Group Behavioural Responses of Atlantic Salmon (Salmo salar L.) to Light, <span class="hlt">Infrasound</span> and Sound Stimuli</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bui, Samantha; Oppedal, Frode; Korsøen, Øyvind J.; Sonny, Damien; Dempster, Tim</p> <p>2013-01-01</p> <p>Understanding species-specific flight behaviours is essential in developing methods of guiding fish spatially, and requires knowledge on how groups of fish respond to aversive stimuli. By harnessing their natural behaviours, the use of physical manipulation or other potentially harmful procedures can be minimised. We examined the reactions of sea-caged groups of 50 salmon (1331±364 g) to short-term exposure to visual or acoustic stimuli. In light experiments, fish were exposed to one of three intensities of blue LED light (high, medium and low) or no light (control). Sound experiments included exposure to <span class="hlt">infrasound</span> (12 Hz), a surface disturbance event, the combination of <span class="hlt">infrasound</span> and surface disturbance, or no stimuli. Groups that experienced light, <span class="hlt">infrasound</span>, and the combination of <span class="hlt">infrasound</span> and surface disturbance treatments, elicited a marked change in vertical distribution, where fish dived to the bottom of the sea-cage for the duration of the stimulus. Light treatments, but not sound, also reduced the total echo-signal strength (indicative of swim bladder volume) after exposure to light, compared to pre-stimulus levels. Groups in <span class="hlt">infrasound</span> and combination treatments showed increased swimming activity during stimulus application, with swimming speeds tripled compared to that of controls. In all light and sound treatments, fish returned to their pre-stimulus swimming depths and speeds once exposure had ceased. This work establishes consistent, short-term avoidance responses to these stimuli, and provides a basis for methods to guide fish for aquaculture applications, or create avoidance barriers for conservation purposes. In doing so, we can achieve the manipulation of group position with minimal welfare impacts, to create more sustainable practices. PMID:23691087</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.2683M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.2683M"><span>Ionosonde tracking of <span class="hlt">infrasound</span> wavefronts in the thermosphere launched by seismic waves after the 2010 M8.8 Chile earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maruyama, Takashi; Yusupov, Kamil; Akchurin, Adel</p> <p>2016-03-01</p> <p>Ionospheric disturbances associated with the M8.8 Chile earthquake (35.91°S, 72.73°W) on 27 February 2010 were <span class="hlt">observed</span> at Kazan, Russia (55.85°N, 48.81°E). Rapid-run ionograms at 1 min intervals exhibited multiple-cusp signatures (MCSs) for more than 30 min, which have been <span class="hlt">observed</span> several times after large earthquakes. The ionospheric disturbances were caused by <span class="hlt">infrasound</span> propagating upward in the atmosphere, which modified the electron density distribution through ion-neutral collisions. The anomaly of the vertical electron density distribution responsible for the MCSs was analyzed by converting the ionogram traces into real height profiles. The density profiles at 1 min intervals allowed the tracking of the vertical propagation of <span class="hlt">infrasound</span> and provided information on parameters of acoustic waves, which was not possible from the previous measurements such as standard ionograms at 5-15 min intervals, HF Doppler soundings, and total electron content using satellite beacon signals. The speed of acoustic waves in the thermosphere was evaluated from the consecutive ionograms with MCSs, and it was found that the thermospheric temperature was slightly higher than that calculated using the Mass Spectrometer and Incoherent Scatter Radar empirical model (NRLMSISE-00).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.4306G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.4306G"><span>Infrasonic and seismic signals from earthquakes and explosions <span class="hlt">observed</span> with Plostina seismo-acoustic array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghica, D.; Ionescu, C.</p> <p>2012-04-01</p> <p>Plostina seismo-acoustic array has been recently deployed by the National Institute for Earth Physics in the central part of Romania, near the Vrancea epicentral area. The array has a 2.5 km aperture and consists of 7 seismic sites (PLOR) and 7 collocated <span class="hlt">infrasound</span> instruments (IPLOR). The array is being used to assess the importance of collocated seismic and acoustic sensors for the purposes of (1) seismic monitoring of the local and regional events, and (2) acoustic measurement, consisting of detection of the <span class="hlt">infrasound</span> events (explosions, mine and quarry blasts, earthquakes, aircraft etc.). This paper focuses on characterization of infrasonic and seismic signals from the earthquakes and explosions (accidental and mining type). Two Vrancea earthquakes with magnitude above 5.0 were selected to this study: one occurred on 1st of May 2011 (MD = 5.3, h = 146 km), and the other one, on 4th October 2011 (MD = 5.2, h = 142 km). The infrasonic signals from the earthquakes have the appearance of the vertical component of seismic signals. Because the mechanism of the infrasonic wave formation is the coupling of seismic waves with the atmosphere, trace velocity values for such signals are compatible with the characteristics of the various seismic phases <span class="hlt">observed</span> with PLOR array. The study evaluates and characterizes, as well, <span class="hlt">infrasound</span> and seismic data recorded from the explosion caused by the military accident produced at Evangelos Florakis Naval Base, in Cyprus, on 11th July 2011. Additionally, seismo-acoustic signals presumed to be related to strong mine and quarry blasts were investigated. Ground truth of mine <span class="hlt">observations</span> provides validation of this interpretation. The combined seismo-acoustic analysis uses two types of detectors for signal identification: one is the automatic detector DFX-PMCC, applied for <span class="hlt">infrasound</span> detection and characterization, while the other one, which is used for seismic data, is based on array processing techniques (beamforming and frequency</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21576566','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21576566"><span>LUMINOSITY FUNCTIONS AND POINT-<span class="hlt">SOURCE</span> PROPERTIES FROM MULTIPLE CHANDRA <span class="hlt">OBSERVATIONS</span> OF M81</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sell, P. H.; Pooley, D.; Heinz, S.; Zezas, A.; Homan, J.; Lewin, W. H. G.</p> <p>2011-07-01</p> <p>We present an analysis of 15 Chandra <span class="hlt">observations</span> of the nearby spiral galaxy M81 taken over the course of six weeks in 2005 May-July. Each <span class="hlt">observation</span> reaches a sensitivity of {approx}10{sup 37} erg s{sup -1}. With these <span class="hlt">observations</span> and one previous deeper Chandra <span class="hlt">observation</span>, we compile a master <span class="hlt">source</span> list of 265 point <span class="hlt">sources</span>, extract and fit their spectra, and differentiate basic populations of <span class="hlt">sources</span> through their colors. We also carry out variability analyses of individual point <span class="hlt">sources</span> and of X-ray luminosity functions (XLFs) in multiple regions of M81 on timescales of days, months, and years. We find that, despite measuring significant variability in a considerable fraction of <span class="hlt">sources</span>, snapshot <span class="hlt">observations</span> provide a consistent determination of the XLF of M81. We also fit the XLFs for multiple regions of M81 and, using common parameterizations, compare these luminosity functions to those of two other spiral galaxies, M31 and the Milky Way.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711869J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711869J"><span><span class="hlt">Infrasound</span> network implementation in Iceland - examples of volcano monitoring in an extreme environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jónsdóttir, Kristín; Ripepe, Maurizio; Barsotti, Sara; Björnsson, Halldór; Del Donne, Dario; Vogfjörð, Kristín</p> <p>2015-04-01</p> <p>The installation of a network of <span class="hlt">infrasound</span> arrays for volcano monitoring has been initiated in Iceland. In collaboration with the University of Florence (UNIFI), The Icelandic Meteorological Office (IMO) has been operating <span class="hlt">infrasound</span> arrays since the Eyjafjallajökull eruption in 2010. An important support came through the 26 partner FP7 FUTUREVOLC project which runs from 2012 - 2016. This project which is relevant to the EU "Supersite concept" for long term monitoring in geologically active regions of Europe, is led by the University of Iceland together with IMO which leads long-term monitoring of geohazards in Iceland and is responsible for maintaining instrument networks for this purpose. As a part of the ground based FUTUREVOLC network, <span class="hlt">infrasound</span> arrays, are used to monitor volcanic eruptive activity. The arrays are composed of 4 elements with a triangular geometry and an aperture of 120 m where each element has a differential pressure transducer with a sensitivity of 25 mV/Pa in the frequency band 0.001-50 Hz and a noise level of 10-2 Pa. <span class="hlt">Infrasound</span> is recorded on site at 100 Hz and 24 bits and transmitted via Internet link both to the IMO and UNIFI. Three arrays are installed in South Iceland, one in Gunnarsholt, one in Þjórsárdalur and one in Kirkjubæjarklaustur. These places were chosen with the aim to optimize wind noice reduction (onsite bushes and trees) and close proximity to volcanoes such as Hekla, Katla, Torfajökull, Eyjafjallajökull, Vestmannaeyjar and the Vatnajökull ice cap which covers four central volcanoes known for explosive eruptions. In September 2014, the fourth array was installed a few km north of Vatnajökull glacier, just north of the large effusive eruption in Holuhraun which started on 29 August 2014 and is still ongoing in January 2015. The eruption is associated with the ongoing Bárðarbunga volcanic unrest and caldera collapse which is being monitored closely by the IMO and FUTUREVOLC partners. The new array has the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780037753&hterms=infrared+spectrophotometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dinfrared%2Bspectrophotometry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780037753&hterms=infrared+spectrophotometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dinfrared%2Bspectrophotometry"><span>Infrared <span class="hlt">observations</span> of the galactic center. I - Nature of the compact <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Becklin, E. E.; Matthews, K.; Neugebauer, G.; Willner, S. P.</p> <p>1978-01-01</p> <p>Photometry from 1.25 to 12 micrometers and spectrophotometry from 8 to 13 micrometers of the compact <span class="hlt">sources</span> found in the galactic-center region are reported. In addition, revised 10 and new 20 micrometers maps with 2''.3 resolution are given. The nature of the compact <span class="hlt">sources</span> is discussed. Some are best identified as stars or star clusters; the brightest <span class="hlt">source</span> at 2 micrometers is probably a supergiant, and the infrared <span class="hlt">source</span> near the nonthermal radio <span class="hlt">source</span> is probably a stellar cluster with density greater than 1 million solar masses/cu pc. Other <span class="hlt">sources</span> emit most of their luminosity at wavelengths of 10 micrometers and greater; this emission is probably from heated dust. One of the <span class="hlt">sources</span> is <span class="hlt">observationally</span> similar to extremely red OH/infrared stars. Other <span class="hlt">sources</span> have luminosities and linear sizes similar to those of compact H II regions; emission from optically thin silicate dust is seen in these.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA530075','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA530075"><span>Seismic <span class="hlt">Observations</span> and Interpretation in NE China, <span class="hlt">Infrasound</span> <span class="hlt">Observations</span> and Interpretation in Utah</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2010-07-30</p> <p>from Xu et al., 2005). (b) Map of SMU-IGPCEA Huailai Seismic Network and seismicity (open circles) for the time period of January 01, 2002 through...stations BGU and NOQ have broadband instruments, and EPU is a short- period seismic station. The amplitude scales are different and the seismic signal at...structures including the two bounding E-W orogenic belts and crustal thickening before the late Jurassic . The second phase of deformation is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AJ....152..151X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AJ....152..151X"><span>The <span class="hlt">Source</span> Structure of 0642+449 Detected from the CONT14 <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Ming H.; Heinkelmann, Robert; Anderson, James M.; Mora-Diaz, Julian; Schuh, Harald; Wang, Guang L.</p> <p>2016-11-01</p> <p>The CONT14 campaign with state-of-the-art very long baseline interferometry (VLBI) data has <span class="hlt">observed</span> the <span class="hlt">source</span> 0642+449 with about 1000 <span class="hlt">observables</span> each day during a continuous <span class="hlt">observing</span> period of 15 days, providing tens of thousands of closure delays—the sum of the delays around a closed loop of baselines. The closure delay is independent of the instrumental and propagation delays and provides valuable additional information about the <span class="hlt">source</span> structure. We demonstrate the use of this new “observable” for the determination of the structure in the radio <span class="hlt">source</span> 0642+449. This <span class="hlt">source</span>, as one of the defining <span class="hlt">sources</span> in the second realization of the International Celestial Reference Frame, is found to have two point-like components with a relative position offset of -426 microarcseconds (μas) in R.A. and -66 μas in decl. The two components are almost equally bright, with a flux-density ratio of 0.92. The standard deviation of closure delays for <span class="hlt">source</span> 0642+449 was reduced from 139 to 90 ps by using this two-component model. Closure delays larger than 1 ns are found to be related to the <span class="hlt">source</span> structure, demonstrating that structure effects for a <span class="hlt">source</span> with this simple structure could be up to tens of nanoseconds. The method described in this paper does not rely on a priori <span class="hlt">source</span> structure information, such as knowledge of <span class="hlt">source</span> structure determined from direct (Fourier) imaging of the same <span class="hlt">observations</span> or <span class="hlt">observations</span> at other epochs. We anticipate our study to be a starting point for more effective determination of the structure effect in VLBI <span class="hlt">observations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22365559','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22365559"><span>JVLA <span class="hlt">observations</span> of IC 348 SW: Compact radio <span class="hlt">sources</span> and their nature</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rodríguez, Luis F.; Zapata, Luis A.; Palau, Aina E-mail: l.zapata@crya.unam.mx</p> <p>2014-07-20</p> <p>We present sensitive 2.1 and 3.3 cm Jansky Very Large Array radio continuum <span class="hlt">observations</span> of the region IC 348 SW. We detect a total of 10 compact radio <span class="hlt">sources</span> in the region, 7 of which are first reported here. One of the <span class="hlt">sources</span> is associated with the remarkable periodic time-variable infrared <span class="hlt">source</span> LRLL 54361, opening the possibility of monitoring this object at radio wavelengths. Four of the <span class="hlt">sources</span> appear to be powering outflows in the region, including HH 211 and HH 797. In the case of the rotating outflow HH 797, we detect a double radio <span class="hlt">source</span> at its center, separated by ∼3''. Two of the <span class="hlt">sources</span> are associated with infrared stars that possibly have gyrosynchrotron emission produced in active magnetospheres. Finally, three of the <span class="hlt">sources</span> are interpreted as background objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvD..90d3005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvD..90d3005A"><span>Pinpointing extragalactic neutrino <span class="hlt">sources</span> in light of recent IceCube <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahlers, Markus; Halzen, Francis</p> <p>2014-08-01</p> <p>The IceCube Collaboration has recently reported the <span class="hlt">observation</span> of a flux of high-energy astrophysical neutrinos. The angular distribution of events is consistent with an isotropic arrival direction of neutrinos which is expected for an extragalactic origin. We estimate the prospects of detecting individual neutrino <span class="hlt">sources</span> from a quasidiffuse superposition of many extragalactic <span class="hlt">sources</span> at the level of the IceCube <span class="hlt">observation</span>. Unlike previous analyses, we take into account ensemble variations of the <span class="hlt">source</span> distribution as well as the event statistics of individual <span class="hlt">sources</span>. We show that IceCube in its present configuration is sensitive to rare ≲10-8 Mpc-3 yr-1 transient <span class="hlt">source</span> classes within five years of operation via the <span class="hlt">observation</span> of event clusters. Identification of time-independent <span class="hlt">sources</span> is more challenging due to larger backgrounds. We estimate that during the same period IceCube is sensitive to sparse <span class="hlt">sources</span> with densities of ≲10-6 Mpc-3 via association of events with the closest 100 <span class="hlt">sources</span> of an ensemble. We show that a next-generation neutrino observatory with 5 times the effective area of IceCube and otherwise similar detector performance would increase the sensitivity to <span class="hlt">source</span> densities and rates by about 2 orders of magnitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED562869.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED562869.pdf"><span>Using Generalizability Theory to Examine <span class="hlt">Sources</span> of Variance in <span class="hlt">Observed</span> Behaviors within High School Classrooms</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Abry, Tashia; Cash, Anne H.; Bradshaw, Catherine P.</p> <p>2014-01-01</p> <p>Generalizability theory (GT) offers a useful framework for estimating the reliability of a measure while accounting for multiple <span class="hlt">sources</span> of error variance. The purpose of this study was to use GT to examine multiple <span class="hlt">sources</span> of variance in and the reliability of school-level teacher and high school student behaviors as <span class="hlt">observed</span> using the tool,…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.6324J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.6324J"><span>Lahar <span class="hlt">infrasound</span> associated with Volcán Villarrica's 3 March 2015 eruption</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnson, Jeffrey B.; Palma, Jose L.</p> <p>2015-08-01</p> <p>The paroxysmal 2015 eruption of Volcán Villarrica (Chile) produced a 2.5 h long lahar, which descended more than 20 km within the Rio Correntoso/Turbio drainage and destroyed two small bridges. A three-element <span class="hlt">infrasound</span> array 10 km from the summit, and 4 km from the lahar's closest approach, was used to study the flow's progression. Array processing using cross-correlation lag times and semblance places constraints on the lahar's dynamics, including detection of an initial flow pulse that traveled from 2 to 12 km at an average speed of 38 m/s. Subsequently, the lahar signal evolved to a relatively stationary infrasonic tremor located 10 to 12 km from the vent and adjacent to a topographic notch, through which sound may have preferentially diffracted toward the recording site. This study demonstrates the powerful capabilities of <span class="hlt">infrasound</span> arrays for lahar study and suggests their potential application for future hazard monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatSR...4E6105K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatSR...4E6105K"><span>Nanotube Aerogel Sheet Flutter for Actuation, Power Generation, and <span class="hlt">Infrasound</span> Detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kang, Tae June; Kim, Taewoo; Jang, Eui Yun; Im, Hyeongwook; Lepro-Chavez, Xavier; Ovalle-Robles, Raquel; Oh, Jiyoung; Kozlov, Mikhail E.; Baughman, Ray H.; Lee, Hong H.; Kim, Yong Hyup</p> <p>2014-08-01</p> <p>Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect <span class="hlt">infrasound</span> at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for <span class="hlt">infrasound</span> frequencies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4135338','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4135338"><span>Nanotube Aerogel Sheet Flutter for Actuation, Power Generation, and <span class="hlt">Infrasound</span> Detection</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kang, Tae June; Kim, Taewoo; Jang, Eui Yun; Im, Hyeongwook; Lepro-Chavez, Xavier; Ovalle-Robles, Raquel; Oh, Jiyoung; Kozlov, Mikhail E.; Baughman, Ray H.; Lee, Hong H.; Kim, Yong Hyup</p> <p>2014-01-01</p> <p>Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect <span class="hlt">infrasound</span> at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for <span class="hlt">infrasound</span> frequencies. PMID:25130708</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S23B2510M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S23B2510M"><span>Optimizing an <span class="hlt">infrasound</span> sensor network for measuring acoustic background noise and its inversion for stratospheric winds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marcillo, O. E.; Arrowsmith, S.</p> <p>2013-12-01</p> <p>We demonstrate the design of an <span class="hlt">infrasound</span> network (and the associated analysis) for measuring and inverting low-frequency acoustic background noise (microbaroms) for stratospheric winds. We developed a mathematical framework for the inversion of local stratospheric winds using microbaroms, and found theoretical constraints on the optimum sensor network topology. Based on these results, we deployed, over the winter months (January to March, 2013), a prototype sensor network comprising six <span class="hlt">infrasound</span> stations separated between 5 and 70 km; the initial analysis shows periods of very high coherency (suitable for our inversion) lasting several hours with associated tropospheric and low stratospheric celerities. We are analyzing the coherency between signals with distance and relative azimuth. Following this pilot study, we are designing a denser sensor network further optimized to capture microbaroms and planning for its validation using independent measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090023877','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090023877"><span>Chemical <span class="hlt">Source</span> Inversion using Assimilated Constituent <span class="hlt">Observations</span> in an Idealized Two-dimensional System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tangborn, Andrew; Cooper, Robert; Pawson, Steven; Sun, Zhibin</p> <p>2009-01-01</p> <p>We present a <span class="hlt">source</span> inversion technique for chemical constituents that uses assimilated constituent <span class="hlt">observations</span> rather than directly using the <span class="hlt">observations</span>. The method is tested with a simple model problem, which is a two-dimensional Fourier-Galerkin transport model combined with a Kalman filter for data assimilation. Inversion is carried out using a Green's function method and <span class="hlt">observations</span> are simulated from a true state with added Gaussian noise. The forecast state uses the same spectral spectral model, but differs by an unbiased Gaussian model error, and emissions models with constant errors. The numerical experiments employ both simulated in situ and satellite <span class="hlt">observation</span> networks. <span class="hlt">Source</span> inversion was carried out by either direct use of synthetically generated <span class="hlt">observations</span> with added noise, or by first assimilating the <span class="hlt">observations</span> and using the analyses to extract <span class="hlt">observations</span>. We have conducted 20 identical twin experiments for each set of <span class="hlt">source</span> and <span class="hlt">observation</span> configurations, and find that in the limiting cases of a very few localized <span class="hlt">observations</span>, or an extremely large <span class="hlt">observation</span> network there is little advantage to carrying out assimilation first. However, in intermediate <span class="hlt">observation</span> densities, there decreases in <span class="hlt">source</span> inversion error standard deviation using the Kalman filter algorithm followed by Green's function inversion by 50% to 95%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.460.3829M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.460.3829M"><span>Swift <span class="hlt">observations</span> of unidentified radio <span class="hlt">sources</span> in the revised Third Cambridge Catalogue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maselli, A.; Massaro, F.; Cusumano, G.; La Parola, V.; Harris, D. E.; Paggi, A.; Liuzzo, E.; Tremblay, G. R.; Baum, S. A.; O'Dea, C. P.</p> <p>2016-08-01</p> <p>We have investigated a group of unassociated radio <span class="hlt">sources</span> included in the Third Cambridge Catalogue (3CR) to increase the multifrequency information on them and possibly obtain an identification. We have carried out an <span class="hlt">observational</span> campaign with the Swift satellite to <span class="hlt">observe</span> with the Ultraviolet/Optical Telescope (UVOT) and the X-Ray Telescope (XRT) the field of view of 21 bright NRAO VLA Sky Survey (NVSS) <span class="hlt">sources</span> within the positional uncertainty region of the 3CR <span class="hlt">sources</span>. Furthermore, we have searched in the recent AllWISE <span class="hlt">Source</span> Catalogue for infrared <span class="hlt">sources</span> matching the position of these NVSS <span class="hlt">sources</span>. We have detected significant emission in the soft X-ray band for nine of the investigated NVSS <span class="hlt">sources</span>. To all of them, and in four cases with no soft X-ray association, we have associated a Wide-field Infrared Survey Explorer infrared counterpart. Eight of these infrared candidates have not been proposed earlier in the literature. In the five remaining cases our candidate matches one among a few optical candidates suggested for the same 3CR <span class="hlt">source</span> in previous studies. No <span class="hlt">source</span> has been detected in the UVOT filters at the position of the NVSS objects, confirming the scenario that all of them are heavily obscured. With this in mind, a spectroscopic campaign, preferably in the infrared band, will be necessary to establish the nature of the <span class="hlt">sources</span> that we have finally identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985ApJ...295..134F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985ApJ...295..134F"><span>VLBI <span class="hlt">observations</span> at 22.2 gigahertz of the radio <span class="hlt">source</span> 0552 + 398 (DA 193)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fey, A. L.; Spangler, S. R.; Mutel, R. L.; Benson, J. M.</p> <p>1985-08-01</p> <p>The authors report 22.2 GHz <span class="hlt">observations</span> of the quasar 0552+398 (DA 193). The data are used to refine the <span class="hlt">source</span> structure model and magnetic field estimate previously reported by Spangler and colleagues in 1983. The <span class="hlt">source</span> is found to be more compact and the magnetic field to be weaker than indicated by the previous <span class="hlt">observations</span>. It is suggested that the object may be considered a highly compact, "naked core" object.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770015077','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770015077"><span><span class="hlt">Observation</span> of the X-ray <span class="hlt">source</span> Sco X-1 from Skylab. [radiant flux density</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, R. M.</p> <p>1977-01-01</p> <p>An attempt to <span class="hlt">observe</span> the discrete X-ray <span class="hlt">source</span> Sco X-1 on 20 September 1973 between 0856 and 0920 UT is reported. Data obtained with the ATM/S-056 X-ray event analyzer, in particular the flux <span class="hlt">observed</span> with the 1.71 to 4.96 KeV counter, is analyzed. No photographic image of the <span class="hlt">source</span> was obtained because Sco X-1 was outside the field of view of the X-ray telescope.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850025652','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850025652"><span>Radio <span class="hlt">observations</span> of four anticenter 2CG gamma-ray <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oezel, M. E.; Schlickeiser, R.; Sieber, W.</p> <p>1985-01-01</p> <p>The 2CG <span class="hlt">sources</span> 218-00, 135+01, 121+04 and 95+04 have been <span class="hlt">observed</span> at two radio frequencies and the flux values and spectra of the radio <span class="hlt">sources</span> <span class="hlt">observed</span> within the gamma-ray fields are catalogued down to a sensitivity of approx 30 mJy at lambda 11 cm. Possible gamma-ray counterpart candidate objects are briefly discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917497S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917497S"><span>Automatic identification of alpine mass movements based on seismic and <span class="hlt">infrasound</span> signals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schimmel, Andreas; Hübl, Johannes</p> <p>2017-04-01</p> <p>The automatic detection and identification of alpine mass movements like debris flows, debris floods or landslides gets increasing importance for mitigation measures in the densely populated and intensively used alpine regions. Since this mass movement processes emits characteristically seismic and acoustic waves in the low frequency range this events can be detected and identified based on this signals. So already several approaches for detection and warning systems based on seismic or <span class="hlt">infrasound</span> signals has been developed. But a combination of both methods, which can increase detection probability and reduce false alarms is currently used very rarely and can serve as a promising method for developing an automatic detection and identification system. So this work presents an approach for a detection and identification system based on a combination of seismic and <span class="hlt">infrasound</span> sensors, which can detect sediment related mass movements from a remote location unaffected by the process. The system is based on one <span class="hlt">infrasound</span> sensor and one geophone which are placed co-located and a microcontroller where a specially designed detection algorithm is executed which can detect mass movements in real time directly at the sensor site. Further this work tries to get out more information from the seismic and <span class="hlt">infrasound</span> spectrum produced by different sediment related mass movements to identify the process type and estimate the magnitude of the event. The system is currently installed and tested on five test sites in Austria, two in Italy and one in Switzerland as well as one in Germany. This high number of test sites is used to get a large database of very different events which will be the basis for a new identification method for alpine mass movements. These tests shows promising results and so this system provides an easy to install and inexpensive approach for a detection and warning system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA590009','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA590009"><span>Detection Optimization of the Progressive Multi-Channel Correlation Algorithm Used in <span class="hlt">Infrasound</span> Nuclear Treaty Monitoring</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-03-01</p> <p>microbaroms, mountain associated waves, volcanic eruptions , auroras, earthquakes, rockets, and explosions [5] [6]. Examination of <span class="hlt">infrasound</span> dating...progressive search for distant sensors to add to initial sub- arrays, a PMCC pitfall more comprehensively addressed in Section 2.3. WinPMCC’s solution to this...the goal is to minimize the total number of false alarm and missed detection categorization decisions. Specifically, the solution to this approach</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27475150','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27475150"><span>Detection of regional <span class="hlt">infrasound</span> signals using array data: Testing, tuning, and physical interpretation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Park, Junghyun; Stump, Brian W; Hayward, Chris; Arrowsmith, Stephen J; Che, Il-Young; Drob, Douglas P</p> <p>2016-07-01</p> <p>This work quantifies the physical characteristics of <span class="hlt">infrasound</span> signal and noise, assesses their temporal variations, and determines the degree to which these effects can be predicted by time-varying atmospheric models to estimate array and network performance. An automated detector that accounts for both correlated and uncorrelated noise is applied to <span class="hlt">infrasound</span> data from three seismo-acoustic arrays in South Korea (BRDAR, CHNAR, and KSGAR), cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU). Arrays located on an island and near the coast have higher noise power, consistent with both higher wind speeds and seasonably variable ocean wave contributions. On the basis of the adaptive F-detector quantification of time variable environmental effects, the time-dependent scaling variable is shown to be dependent on both weather conditions and local site effects. Significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, detection numbers, and phase velocity/azimuth estimates are documented. These time-dependent effects are strongly correlated with atmospheric winds and temperatures and are predicted by available atmospheric specifications. This suggests that commonly available atmospheric specifications can be used to predict both station and network detection performance, and an appropriate forward model improves location capabilities as a function of time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1326653-detection-regional-infrasound-signals-using-array-data-testing-tuning-physical-interpretation','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1326653-detection-regional-infrasound-signals-using-array-data-testing-tuning-physical-interpretation"><span>Detection of regional <span class="hlt">infrasound</span> signals using array data: Testing, tuning, and physical interpretation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Park, Junghyun; Stump, Brian W.; Hayward, Chris; ...</p> <p>2016-07-14</p> <p>This work quantifies the physical characteristics of <span class="hlt">infrasound</span> signal and noise, assesses their temporal variations, and determines the degree to which these effects can be predicted by time-varying atmospheric models to estimate array and network performance. An automated detector that accounts for both correlated and uncorrelated noise is applied to <span class="hlt">infrasound</span> data from three seismo-acoustic arrays in South Korea (BRDAR, CHNAR, and KSGAR), cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU). Arrays located on an island and near the coast have higher noise power, consistent with both higher wind speeds and seasonablymore » variable ocean wave contributions. On the basis of the adaptive F-detector quantification of time variable environmental effects, the time-dependent scaling variable is shown to be dependent on both weather conditions and local site effects. Significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, detection numbers, and phase velocity/azimuth estimates are documented. These time-dependent effects are strongly correlated with atmospheric winds and temperatures and are predicted by available atmospheric specifications. As a result, this suggests that commonly available atmospheric specifications can be used to predict both station and network detection performance, and an appropriate forward model improves location capabilities as a function of time.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19045635','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19045635"><span>Finite-difference time-domain synthesis of <span class="hlt">infrasound</span> propagation through an absorbing atmosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Groot-Hedlin, C</p> <p>2008-09-01</p> <p>Equations applicable to finite-difference time-domain (FDTD) computation of <span class="hlt">infrasound</span> propagation through an absorbing atmosphere are derived and examined in this paper. It is shown that over altitudes up to 160 km, and at frequencies relevant to global <span class="hlt">infrasound</span> propagation, i.e., 0.02-5 Hz, the acoustic absorption in dB/m varies approximately as the square of the propagation frequency plus a small constant term. A second-order differential equation is presented for an atmosphere modeled as a compressible Newtonian fluid with low shear viscosity, acted on by a small external damping force. It is shown that the solution to this equation represents pressure fluctuations with the attenuation indicated above. Increased dispersion is predicted at altitudes over 100 km at <span class="hlt">infrasound</span> frequencies. The governing propagation equation is separated into two partial differential equations that are first order in time for FDTD implementation. A numerical analysis of errors inherent to this FDTD method shows that the attenuation term imposes additional stability constraints on the FDTD algorithm. Comparison of FDTD results for models with and without attenuation shows that the predicted transmission losses for the attenuating media agree with those computed from synthesized waveforms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23862892','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23862892"><span>Computationally robust and noise resistant numerical detector for the detection of atmospheric <span class="hlt">infrasound</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Dong-Chang; Olson, John V; Szuberla, Curt A L</p> <p>2013-07-01</p> <p>This work reports on a performance study of two numerical detectors that are particularly useful for <span class="hlt">infrasound</span> arrays operating under windy conditions. The sum of squares of variance ratios (SSVR1)-proposed for detecting signals with frequency ranging from 1 to 10 Hz-is computed by taking the ratio of the squared sum of eigenvalues to the square of largest eigenvalue of the covariance matrix of the power spectrum. For signals with lower frequency between 0.015 and 0.1 Hz, SSVR2 is developed to reduce the detector's sensitivity to noise. The detectors' performances are graphically compared against the current method, the mean of cross correlation maxima (MCCM), using the receiver operating characteristics curves and three types of atmospheric <span class="hlt">infrasound</span>, corrupted by Gaussian and Pink noise. The MCCM and SSVR2 detectors were also used to detect microbaroms from the 24 h-long <span class="hlt">infrasound</span> data. It was found that the two detectors outperform the MCCM detector in both sensitivity and computational efficiency. For mine blasts corrupted by Pink noise (signal-to-noise ratio = -7 dB), the MCCM and SSVR1 detectors yield 62 and 88 % true positives when accepting 20% false positives. For an eight-sensor array, the speed gain is approximately eleven-fold for a 50 s long signal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1326653','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1326653"><span>Detection of regional <span class="hlt">infrasound</span> signals using array data: Testing, tuning, and physical interpretation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Park, Junghyun; Stump, Brian W.; Hayward, Chris; Arrowsmith, Stephen J.; Che, Il-Young; Drob, Douglas P.</p> <p>2016-07-14</p> <p>This work quantifies the physical characteristics of <span class="hlt">infrasound</span> signal and noise, assesses their temporal variations, and determines the degree to which these effects can be predicted by time-varying atmospheric models to estimate array and network performance. An automated detector that accounts for both correlated and uncorrelated noise is applied to <span class="hlt">infrasound</span> data from three seismo-acoustic arrays in South Korea (BRDAR, CHNAR, and KSGAR), cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU). Arrays located on an island and near the coast have higher noise power, consistent with both higher wind speeds and seasonably variable ocean wave contributions. On the basis of the adaptive F-detector quantification of time variable environmental effects, the time-dependent scaling variable is shown to be dependent on both weather conditions and local site effects. Significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, detection numbers, and phase velocity/azimuth estimates are documented. These time-dependent effects are strongly correlated with atmospheric winds and temperatures and are predicted by available atmospheric specifications. As a result, this suggests that commonly available atmospheric specifications can be used to predict both station and network detection performance, and an appropriate forward model improves location capabilities as a function of time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1326653','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1326653"><span>Detection of regional <span class="hlt">infrasound</span> signals using array data: Testing, tuning, and physical interpretation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Park, Junghyun; Stump, Brian W.; Hayward, Chris; Arrowsmith, Stephen J.; Che, Il-Young; Drob, Douglas P.</p> <p>2016-07-14</p> <p>This work quantifies the physical characteristics of <span class="hlt">infrasound</span> signal and noise, assesses their temporal variations, and determines the degree to which these effects can be predicted by time-varying atmospheric models to estimate array and network performance. An automated detector that accounts for both correlated and uncorrelated noise is applied to <span class="hlt">infrasound</span> data from three seismo-acoustic arrays in South Korea (BRDAR, CHNAR, and KSGAR), cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU). Arrays located on an island and near the coast have higher noise power, consistent with both higher wind speeds and seasonably variable ocean wave contributions. On the basis of the adaptive F-detector quantification of time variable environmental effects, the time-dependent scaling variable is shown to be dependent on both weather conditions and local site effects. Significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, detection numbers, and phase velocity/azimuth estimates are documented. These time-dependent effects are strongly correlated with atmospheric winds and temperatures and are predicted by available atmospheric specifications. As a result, this suggests that commonly available atmospheric specifications can be used to predict both station and network detection performance, and an appropriate forward model improves location capabilities as a function of time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990063839&hterms=open+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dopen%2Bsource','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990063839&hterms=open+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dopen%2Bsource"><span><span class="hlt">Source</span> Distributions of Substorm Ions <span class="hlt">Observed</span> in the Near-Earth Magnetotail</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ashour-Abdalla, M.; El-Alaoui, M.; Peroomian, V.; Walker, R. J.; Raeder, J.; Frank, L. A.; Paterson, W. R.</p> <p>1999-01-01</p> <p>This study employs Geotail plasma <span class="hlt">observations</span> and numerical modeling to determine <span class="hlt">sources</span> of the ions <span class="hlt">observed</span> in the near-Earth magnetotail near midnight during a substorm. The growth phase has the low-latitude boundary layer as its most important <span class="hlt">source</span> of ions at Geotail, but during the expansion phase the plasma mantle is dominant. The mantle distribution shows evidence of two distinct entry mechanisms: entry through a high latitude reconnection region resulting in an accelerated component, and entry through open field lines traditionally identified with the mantle <span class="hlt">source</span>. The two entry mechanisms are separated in time, with the high-latitude reconnection region disappearing prior to substorm onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920046806&hterms=monsters&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmonsters','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920046806&hterms=monsters&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmonsters"><span>VLA <span class="hlt">observations</span> of radio <span class="hlt">sources</span> in interacting galaxy pairs in poor clusters</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Batuski, David J.; Hanisch, Robert J.; Burns, Jack O.</p> <p>1992-01-01</p> <p><span class="hlt">Observations</span> of 16 radio <span class="hlt">sources</span> in interacting galaxies in 14 poor clusters were made using the Very Large Array in the B configuration at lambda of 6 and 2 cm. These <span class="hlt">sources</span> had been unresolved in earlier <span class="hlt">observations</span> at lambda of 21 cm, and were chosen as a sample to determine which of three models for radio <span class="hlt">source</span> formation actually pertains in interacting galaxies. From the analysis of this sample, the starburst model appears most successful, but the 'central monster' model could pertain in some cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920046806&hterms=Monsters&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMonsters','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920046806&hterms=Monsters&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMonsters"><span>VLA <span class="hlt">observations</span> of radio <span class="hlt">sources</span> in interacting galaxy pairs in poor clusters</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search