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Sample records for infrasound source observed

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. Vent geometry detected from infrasound observation on Villaricca volcano, Chile

    NASA Astrophysics Data System (ADS)

    Goto, A.; Johnson, J. B.; Sanderson, R. W.; Anderson, J.; Varley, N. R.

    2010-12-01

    Volcan Villarrica in the southern Andes, Chile, is an active stratovolcano that hosts a convecting lava lake in the summit crater. Activity is characterized by persistent degassing and bubble bursting at the surface of lava lake. Between the 21st and 23rd of Jan 2010 we recorded monotonic infrasound with a stable dominant frequency at 0.7 to 0.8 Hz. Associated video imagery of the active lava lake, taken by a camera suspended from a wire across the crater, showed active convection and degassing, but gas release events were not directly correlated with infrasound transients. Continuous monotonic infrasound strongly suggests a resonant phenomena associated with a stable conduit and vent system. In the present study we attempt to estimate the vent geometry of Villarrica volcano based on the observed infrasound. We deployed four stations consisting of infrasound microphones, audible microphone, three components seismometers and weather stations, two of which were on the eastern and western rim of the crater, while the other two were on the flanks of volcano 2.7 and 3.8 km NNW of the crater, respectively. Despite amplitude variations the observed waveforms were very well correlated among the four stations indicating sound originating in the crater. From our video image and the past studies we inferred a cavity between the lava lake and overhanging spatter roof with a skylight in its center. In this case Helmholtz resonance is plausible as the source of observed monotonic infrasound. An idealized Helmholtz resonance model is manifested by a simple harmonic motion of air pistoning within the skylight neck that separates the inner cavity from external atmosphere. The frequenc f is given by: f=(c/2π)(S/VL)1/2 where c is sound velocity, S is neck cross sectional area, L is neck length and V is cavity volume. In the present case L corresponds to skylight depth. In practice, an extra volume proportional to neck radius moves together with the air above and below the neck

  9. Optical observations of meteors generating infrasound-I: Acoustic signal identification and phenomenology

    NASA Astrophysics Data System (ADS)

    Silber, Elizabeth A.; Brown, Peter G.

    2014-11-01

    We analyse infrasound signals from 71 bright meteors/fireballs simultaneously detected by video to investigate the phenomenology and characteristics of meteor-generated near-field infrasound (<300 km) and shock production. A taxonomy for meteor generated infrasound signal classification has been developed using the time-pressure signal of the infrasound arrivals. Based on the location along the meteor trail where the infrasound signal originates, we find most signals are associated with cylindrical shocks, with about a quarter of events evidencing spherical shocks associated with fragmentation episodes and optical flares. The video data indicate that all events with ray launch angles >117° from the trajectory heading are most likely generated by a spherical shock, while infrasound produced by the meteors with ray launch angles ≤117° can be attributed to both a cylindrical line source and a spherical shock. We find that meteors preferentially produce infrasound toward the end of their trails with a smaller number showing a preference for mid-trail production. Meteors producing multiple infrasound arrivals show a strong infrasound source height skewness to the end of trails and are much more likely to be associated with optical flares. We find that about 1% of all our optically-recorded meteors have associated detected infrasound and estimate that regional meteor infrasound events should occur on the order of once per week and dominate in numbers over infrasound associated with more energetic (but rarer) bolides. While a significant fraction of our meteors generating infrasound (~1/4 of single arrivals) are produced by fragmentation events, we find no instances where acoustic radiation is detectable more than about 60° beyond the ballistic regime at our meteoroid sizes (grams to tens of kilograms) emphasizing the strong anisotropy in acoustic radiation for meteors which are dominated by cylindrical line source geometry, even in the presence of fragmentation.

  10. Comparing infrasound measurements of a ground truth source at regional distances with modeling results

    NASA Astrophysics Data System (ADS)

    Streicher, Florian; Wüst, Sabine; Bittner, Michael; Pilger, Christoph; Koch, Karl

    2013-04-01

    The infrasound stations of the International Monitoring System (IMS) have a relatively coarse geographical coverage. Even when taking national infrasound stations which are not part of the IMS into account, the inter-station spacing is still in the range of several hundreds of kilometers. For tasks involving the recovery of dynamic properties of the source and hence the understanding of the atmospheric propagation conditions of the infrasonic waves, it is important to validate the methods applied in infrasound modeling, in particular for shorter distances. The shadow zone that exists for paths between the tropospheric and stratospheric ducts thereby poses the most significant difficulty. A field study has been performed utilizing six single infrasound sensors along the great circle path between a known source (DLR engine test facility, Lampoldshausen) and a nearby receiver (BGR infrasound array I26, Bavarian Forest) covering a distance of about 320km in total. The recordings gathered give new possibilities in studying the evolution of the infrasonic wave-field to regional distances and, in particular, through the shadow zone by comparing measured signals with modeling results. In this study we thus aim at testing and improving our infrasound modeling, especially the prediction of shadow zones in ray-tracing. For numerical modeling the ray-tracer HARPA/DLR is used. Compared to its original version HARPA/DLR was improved by the integration of adequate atmospheric temperature and wind fields (ECMWF weather forecast data for altitudes up to 80km, statistical values given by the MSISE00 (temperature) and HWM07 (horizontal wind) climatologies for greater heights). The modeling shows shadow zones which extend from about 20-40km to some 130-170km for the months from December 2011 to March 2012, in good agreement with the observations. However, the modeling effort for April and May 2012 shows a much broader shadow zone, which is less conforming to the observations. Our

  11. 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.

  12. Trans-Mediterranean Infrasound Propagation in Summer: Theory and Observations

    NASA Astrophysics Data System (ADS)

    Garces, M. A.; Fee, D.; Waxler, R.; Hetzer, C. H.; Assink, J.; Drob, D. P.; Le Pichon, A.; Hofstetter, A.; Gitterman, Y.

    2009-12-01

    The ground surface detonation of ~82 tons of high explosives was successfully conducted on 26 August 2009 by the Geophysical Institute of Israel at the Sayarim Military Range in the Negev desert. The measured detonation time was 6:31:54 GMT, and the GPS coordinates of the surface explosion are 30.00057°N, 34.81351°E, 556 m altitude. The primary goal of the experiment was to transmit low-frequency sound across the Mediterranean to improve our understanding of infrasound propagation in the Middle East and Mediterranean regions. Multiple infrasound arrays were deployed by collaborating institutions, which will also cooperate in the analysis and modeling of the recorded signals. The following organizations participated in temporary infrasound microphone and array deployments in the Mediterranean and Middle East: The Geophysical Institute of Israel and the University of Mississippi (Israel and Cyprus), University of Alaska (Israel), Geological Survey of Cyprus (Cyprus), National Observatory of Athens and University of Hawaii (Rhodes, Crete, and Peloponnese, Greece), University of Florence (Calabria, Italy), CEA/DAM (Provence and Paris, France), and the United Nations (N. Italy, Austria, Germany, and Tunisia). All these station recorded acoustic signals, with ranges from ~100 m (Sayarim, Israel) to ~3500 km (Paris, France). The observations validate the predicted acoustic returns from refraction in the stratosphere and thermosphere during Summer, and are used to further refine sound propagation models and atmospheric specifications.

  13. Peculiar transient phenomena observed by HF Doppler sounding on infrasound time scales

    NASA Astrophysics Data System (ADS)

    Chum, J.; Lastovicka, J.; Sindelárová, T.; Buresová, D.; Hruska, F.

    2008-04-01

    Compared to investigations of the influence of gravity and planetary waves on the ionosphere, the effects of infrasound (periods from about 0.01 s to several minutes) variations have not been studied very much in the last 20 years. Here we present some recent results on peculiar transient phenomena occurring at infrasound timescales, as observed by HF Doppler sounding in the Czech Republic. After a brief description of the measuring equipment for continuous HF Doppler sounding of the ionosphere, we deal with the observations of short-time transient changes that are observed in the Doppler spectrograms in time intervals of a minute or less, and therefore cannot be observed by ionosondes. First, we present examples of S-shaped traces and examine the diurnal and seasonal variation of their occurrence. We show that S-shape phenomena appear to be concentrated near sunset and sunrise. We also discuss the possible source of these disturbances and their relationship to gravity and infrasound waves. Then we show rare patterns with Doppler shifts corresponding to quasi-linear shape (QLS) phenomena in the time-frequency space. Their slope may be positive or negative. We present some of their properties and discuss the possible origin of such a phenomenon. Several potential sources of QLSs were excluded, such as aircrafts, satellites, bolides, meteors, meteorites, thunderstorms or geomagnetic storms. We speculate that QLSs may correspond to the radio waves in the Z-mode reflected at the upper hybrid resonance frequency.

  14. Misty Picture: A Unique Experiment for the Interpretation of the Infrasound Propagation from Large Explosive Sources

    NASA Astrophysics Data System (ADS)

    Gainville, O.; Blanc, E.; Blanc-Benon, P.; Roche, R.; Millet, C.; Le Piver, F.; Piserchia, P.

    2008-12-01

    In the framework of the Comprehensive Nuclear-Test-Ban Treaty, the International Monitoring System develops a 60 micro-barometric stations network. These stations, which records infrasound, detect various powerful natural and artificial sources like long range explosions, oceanic swell, and volcano eruptions. The Misty Picture experiment is a high explosive event (4685 Tons of ANFO) realized in 1987 in New Mexico (US). Infrasound waves were recorded by an amount of 22 sensors installed by the Sandia National Laboratories (J.W. Reed et al., 1977, SAND--87-2978C), the Los Alamos National Laboratories (R.W. Whitaker et al. 1990, 4th LRSP) and the CEA (E. Blanc, 1998, CEA). Multi-reflected tropospheric, stratospheric and thermospheric phases are detected until a distance of 1000 km in a quiet background noise condition. Signals recorded near the source (1 km away) and observed in the geometrical shadow zone (between 150 km and 250 km) are of particular interest. This reference experiment is used to improve our understanding of the atmospheric propagation of infrasound as well as to evaluate our models. Using various methods such as ray tracing and parabolic equation, we investigate effects of the wind, atmospheric absorption, nonlinearity, refraction and scattering by small atmospheric scales on observed phase kinds, their travel time and their waveform.

  15. 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.

  16. Fluid Impact as a Source Mechanism for Surf Infrasound

    NASA Astrophysics Data System (ADS)

    Fee, D.; Garces, M.; McNamara, S.; Aucan, J.; Merrifield, M.

    2006-12-01

    The ability to provide infrasonic estimates of breaking ocean wave height and period in shallow reefs, steep rocky coastlines, and sand beaches has been demonstrated in previous work. Yet defining the source process and isolating the source pressure function remained elusive because of ambiguity introduced by complex coastlines and multiple breaker zones. Due to the steep bathymetry and its proximity to land, the Temae reef in the northeast coast of Moorea island, French Polynesia, provided a well constrained experimental environment where individual breaking waves could be identified and recorded. Synchronous wave height, infrasonic, seismic, and visual recordings of individual waves breaking against the shallow reef ledge were made and correlated. We characterize a possible fluid impact source mechanism for surf infrasound, demonstrate the capability to acoustically track alongshore traveling (peeling) plunging waves, and confirm a relationship between ocean wave height and infrasonic amplitude. Depending on the swell and coastal conditions, estimates of ocean wave period are also possible. We also present preliminary results on near-real-time remote infrasonic monitoring of the surf zone on the North Shore of Oahu, Hawaii, during the 2006-07 Winter high surf season.

  17. 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.

  18. Infrasound observation of seismic events occurring in North Korea

    NASA Astrophysics Data System (ADS)

    Park, Y.; Che, I.; Nam, S.; Kim, Y.; Lee, J.

    2012-12-01

    Seismic events of North Korea were analyzed by using data set from the regional network including 31 seismic stations and 5 seismo-acoustic arrays of Korea Institute of Geoscience and Mineral Resources(KIGAM) and 7 Korea-China joint seismic stations in China. Infrasonic data were analysed using the PMCC method, to detect blast-associated infrasonic signals. Phase velocity and back-azimuth of infrasound signals varied between 250 to 400 m/s and ±10° respectively. Seismo-acoustic analysis was conducted to discriminate 375 events which are 38.1 percent of the total seismic events. More than 60 percent of seismo-acoustic events occurred around the Pyeongyang and Wonsan area of North Korea. In the case of the events occurred in the southeastern part of North Korea, the percentage was relatively small. The seismo-acoustic location were improved by using grid-search method. This method was based the observed travel times and azimuths of infrasonic signals and seismic parameter.

  19. Current Status of Infrasound Pilot Observation at Japanese Islands and SYOWA Antarctica, and Development of New Infrasound Sensor using Optical Sensing Method

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Yamamoto, M.; Kanao, M.

    2009-12-01

    Infrasound is sub audible sound (pressure wave), and that frequency range is cut-off frequency of sound (e.g., 3.21 mHz for 15 degree Celsius isothermal atmosphere) to 20 Hz (that is lowest frequency of human audible band). This frequency range is one of the new horizons of the remote sensing in the Earth’s atmosphere, for example, a large earthquake in Sumatra region generated great Tsunami also produced such kinds of waves in atmosphere and shaking Earth itself by free vibration mode as well as affected even upon the upper atmosphere. Last decade, for the purpose of monitoring nuclear tests, a global infrasound network is constructed by CTBTO. The CTBT-IMS infrasound network has 60 infrasound stations and each station contains at least 4 infrasound sensors (arrayed station), they can detect a some-kiloton TNT level atmospheric explosion in range of some 1000 kilometers. This network is enough for monitoring nuclear tests, but much sparse for detecting and analyzing in detail of natural infrasound phenomena. Observation of infrasound in Japan began in 1980’s by Tahira at Aichi University of Educational with using three arrayed sensors of Chaparral Physics’ Model-2. They reported infrasound waves by volcanic eruptions, ocean waves, earthquakes, airplane passages, etc. Recently, infrasound waves possibly generated by thunders, sprites, fireballs / meteorite fall, and artificial reentry of vehicles, and auroral activities have been reported in several papers. In 2004, we began to study infrasound and discussed with Prof. Tahira, then just after his retirement of his university, these three arrayed sensors tested again at Tohoku University in 2005. Network observation of infrasound is significant in studying geophysical phenomena, however, the sensors are too expensive to buy for further several arrayed stations to distribute in Japan. In 2006, we began to develop new types of infrasound sensors by piezo films and firstly tested in field in 2007, comparing with

  20. Infrasound array observations in the Lützow-Holm Bay region, East Antarctica

    NASA Astrophysics Data System (ADS)

    Murayama, Takahiko; Kanao, Masaki; Yamamoto, Masa-Yuki; Ishihara, Yoshiaki; Matsushima, Takeshi; Kakinami, Yoshihiro

    2015-03-01

    The characteristic features of infrasound waves observed in Antarctica reveal a physical interaction involving surface environmental variations in the continent and the surrounding Southern Ocean. A single infrasound sensor has been making continuous recordings since 2008 at Syowa Station (SYO; 69.0S, 39.6E) in the Lützow-Holm Bay (LHB) of East Antarctica. The continuously recorded data clearly show the contamination of background oceanic signals (microbaroms) throughout all seasons. In austral summer 2013, several field stations with infrasound sensors were established along the coast of the LHB. Two infrasound arrays of different diameters were set up: one at SYO (with a 100-m spacing triangle) and one in the S16 area on the continental ice sheet (with a 1000-m spacing triangle). In addition to these arrays, isolated single stations were deployed at two outcrops in the LHB. These newly established arrays clearly detected the propagation direction and frequency content of microbaroms from the Southern Ocean. Microbarom measurements are a useful tool for characterizing ocean wave climates, complementing other oceanographic and geophysical data from the Antarctic. In addition to the microbaroms, several other remarkable infrasound signals were detected, including regional earthquakes, and airburst shock waves emanating from a meteoroid entering the atmosphere over the Russian Republic on 15 February 2013. Detailed and continuous measurements of infrasound waves in Antarctica could prove to be a new proxy for monitoring regional environmental change as well as temporal climate variations in high southern latitudes.

  1. 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.

  2. Infrasound and Seismic Observation of Hayabusa Reentry as An Artificial Meteorite Fall

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Hiramatsu, Y.; Yamamoto, M.; Furumoto, M.; Fujita, K.

    2011-12-01

    The Hayabusa, the world first sample-return minor body explorer, came back to the Earth, and reentered into the Earth's atmosphere on June 13, 2010. Following the reentries of the Genesis in 2004 and the Stardust in 2006, the return of the Hayabusa Sample Return Capsule (H-SRC) was the third direct reentry event from the interplanetary transfer orbit to the Earth at a velocity of over 11.2 km/s. In addition, it was the world first case of the direct reentry of the spacecraft (H-S/C) itself from the interplanetary transfer orbit. The H-SRC and the H-S/C reentries are very good analogue for studying bolide size meteors and meteorite falls. We, therefore, conducted a ground observation campaign for aspects of meteor sciences. We carried out multi-site ground observations of the Hayabusa reentry in the Woomera Prohibited Area (WPA), Australia. The observations were configured with optical imaging with still and video recordings, spectroscopies, and shockwave detection with infrasound and seismic sensors. In this study, we report details of the infrasound/seismic observations and those results. To detect shockwaves from the H-SRC and the H-S/C, we installed three small aperture infrasound/seismic arrays as the main stations. In addition, we also installed three single component seismic sub stations and an audible sound recorder. The infrasound and seismic sensors clearly recorded sonic boom type shockwaves from the H-SRC and disrupted fragments of the H-S/C itself. The audible recording also detected those shockwave sounds in the human audible band. Positive overpressure values of shockwaves (corresponding to the H-SRC) recorded at three main stations are 1.3 Pa, 1.0 Pa, and 0.7 Pa with the slant distance of 36.9 km, 54.9 km, and 67.8 km (i.e., the source altitude of 36.5 km, 38.9km, and 40.6 km), respectively. These amplitudes of shockwave overpressures are systematically smaller than those of theoretical predictions. We tried to identify the sources of shockwaves

  3. Infrasound Interferometry for Active and Passive Sources: A Synthetic Example for Waves Refracted in the Stratosphere

    NASA Astrophysics Data System (ADS)

    Fricke, J.; Ruigrok, E. N.; Evers, L. G.; El Allouche, N.; Simons, D.; Wapenaar, C. A.

    2012-12-01

    The travel time of infrasound through the stratosphere depends on the temperature profile and the wind speed. These atmospheric conditions can be estimated by determining the travel times between different receivers (microbarometers). Therefore the determination of the travel time of infrasound between different receivers becomes more and more important. An approach to determine the travel time is infrasound interferometry. In this work, the infrasound interferometry is applied to synthetic data of active and passive sources refracted by the stratosphere is tested. The synthetic data were generated with a raytracing model. The inputs of the raytracing model are the atmospheric conditions and a source wavelet. As source wavelet we used blast waves and microbaroms. With the atmospheric conditions and the source wavelet the raytracing model calculates the raypath and the travel time of the infrasound. In order to simulate the measurement of a receiver the rays which reach the receiver need to be found. The rays which propagate from a source to the receiver are called eigen rays. The simulation of the receiver measurements takes into account the travel time along the eigen rays, the attenuation of the different atmospheric layers, the spreading of the rays and the influence of caustics. The simulated measurements of the different receivers are combined to synthetic barograms. Two synthetic experiments were performed with the described model. In the first experiment the interferometry was applied to barograms of active sources like blast waves. The second experiment with microbaroms tests the applicability of interferometry to barograms of passive sources. In the next step infrasound interferometry will be applied to measured barograms. These barograms are measured with the 'Large Aperture Infrasound Array' (LAIA). LAIA is being installed by the Royal Netherlands Meteorological Institute (KNMI) in the framework of the radio-astronomical 'Low Frequency Array' (LOFAR

  4. Infrasound/seismic observation of the Hayabusa reentry: Observations and preliminary results

    NASA Astrophysics Data System (ADS)

    Ishihara, Yoshiaki; Hiramatsu, Yoshihiro; Yamamoto, Masa-yuki; Furumoto, Muneyoshi; Fujita, Kazuhisa

    2012-07-01

    The Hayabusa, the world's first sample-return minor body explorer, returned to the Earth, and reentered the Earth's atmosphere on June 13, 2010. Multi-site ground observations of the Hayabusa reentry were carried out in the Woomera Prohibited Area (WPA), Australia. The ground observations were configured with optical imaging with still and video recordings, spectroscopies, and shockwave detection with infrasound and seismic sensors. At three main stations, we installed small aperture infrasound/seismic arrays, as well as three single component seismic sub stations. The infrasound and seismic sensors clearly recorded sonic-boom-type shockwaves from the Hayabusa Sample Return Capsule (H-SRC) and the disrupted fragments of the Hayabusa Spacecraft (H-S/C) itself. Positive overpressure values of shockwaves (corresponding to the H-SRC) recorded at the three main stations were 1.3 Pa, 1.0 Pa, and 0.7 Pa with slant distances of 36.9 km, 54.9 km, and 67.8 km, respectively. Incident vectors of the shockwave from the H-SRC at all three arrays are estimated by an F-K spectrum and agree well with those predicted. Particle motions of ground motions excited by the shockwave show characteristics of a typical Rayleigh wave.

  5. 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. PMID:24437743

  6. Observing Infrasound and Atmospheric Pressure with the NSF EarthScope USArray Transportable Array

    NASA Astrophysics Data System (ADS)

    Vernon, F. L.; Hedlin, M. A.; Busby, R. W.; Woodward, R.

    2010-12-01

    We are creating a real-time infrasound array whose sensing elements are co-located with the 400 seismic stations in the USArray Transportable Array component of the NSF EarthScope program. This continuously sampled array, of an unprecedented scale, will provide opportunities for groundbreaking and interdisciplinary research in atmospheric acoustics, atmospheric science, and seismology. Such an array will sample mean (absolute) values and fluctuations of the surface air pressure with nominal 70 km station spacing, with a dynamic range of about 7 orders of magnitude, and with a sampling frequency of up to 40 Hz. All samples will be synchronized to UTC. This dense network of infrasound sensors will permit us to study the nature of long-range infrasound propagation from regional to continental distances, and study the sources of infrasound signals, using actual acoustic data, free of concerns about seismic-to-acoustic coupling. All new TA stations deployed starting this fall will have a Quanterra Environmental Processor with internal VTI SCP1000 MEMS barometric pressure gauge, Setra 278 absolute microbarometer, and NCPA Infrasound Microphone. We will present data from field tests and from the newly deployed instrumentation.

  7. 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

  8. Time reversal for localization of sources of infrasound signals in a windy stratified atmosphere.

    PubMed

    Lonzaga, Joel B

    2016-06-01

    Time reversal is used for localizing sources of recorded infrasound signals propagating in a windy, stratified atmosphere. Due to the convective effect of the background flow, the back-azimuths of the recorded signals can be substantially different from the source back-azimuth, posing a significant difficulty in source localization. The back-propagated signals are characterized by negative group velocities from which the source back-azimuth and source-to-receiver (STR) distance can be estimated using the apparent back-azimuths and trace velocities of the signals. The method is applied to several distinct infrasound arrivals recorded by two arrays in the Netherlands. The infrasound signals were generated by the Buncefield oil depot explosion in the U.K. in December 2005. Analyses show that the method can be used to substantially enhance estimates of the source back-azimuth and the STR distance. In one of the arrays, for instance, the deviations between the measured back-azimuths of the signals and the known source back-azimuth are quite large (-1° to -7°), whereas the deviations between the predicted and known source back-azimuths are small with an absolute mean value of <1°. Furthermore, the predicted STR distance is off only by <5% of the known STR distance. PMID:27369127

  9. 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.

  10. Network-based evaluation of infrasound source location at Sakurajima Volcano, Japan

    NASA Astrophysics Data System (ADS)

    McKee, K. F.; Fee, D.; Rowell, C. R.; Johnson, J. B.; Yokoo, A.; Matoza, R. S.

    2013-12-01

    An important step in advancing the science and application of volcano infrasound is improved source location and characterization. Here we evaluate different network-based infrasonic source location methods, primarily srcLoc and semblance, using data collected at Sakurajima Volcano, Japan in July 2013. We investigate these methods in 2- and 3-dimensions to assess the necessity of considering 3-D sensor and vent locations. In addition, we compare source locations found using array back azimuth projection from dual arrays. The effect of significant local topography on source location will also be evaluated. Preliminary analysis indicates periods of high- and low-level activity, suggesting different processes occurring in the upper conduit and vent. Network processing will be applied to determine signal versus noise, a technique which illuminates when the volcano is producing infrasound, to further investigate these processes. We combine this with other methods to identify the number and style of eruptions. By bringing together source location, timing of activity level, type of activity (such as tremor, explosions, etc.), and number of events, we aim to improve understanding of the activity and associated infrasound signals at Sakurajima Volcano.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Improved Bayesian Infrasonic Source Localization for regional infrasound

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The mathematical framework used in 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. 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. 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.

  17. 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.

  18. Improved Bayesian Infrasonic Source Localization for regional infrasound

    DOE PAGESBeta

    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

  19. 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

  20. Studies of infrasound propagation using the USArray seismic network (Invited)

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Although there are currently ~ 100 infrasound arrays worldwide, more than ever before, the station density is still insufficient to provide validation for detailed propagation modeling. Much structure in the atmosphere is short-lived and occurs at spatial scales much smaller than the average distance between infrasound stations. Relatively large infrasound signals can be observed on seismic channels due to coupling at the Earth's surface. Recent research, using data from the 70-km spaced 400-station USArray and other seismic network deployments, has shown the value of dense seismic network data for filling in the gaps between infrasound arrays. The dense sampling of the infrasound wavefield has allowed us to observe complete travel-time branches of infrasound signals and shed more light on the nature of infrasound propagation. We present early results from our studies of impulsive atmospheric sources, such as series of UTTR rocket motor detonations in Utah. The Utah blasts have been well recorded by USArray seismic stations and infrasound arrays in Nevada and Washington State. Recordings of seismic signals from a series of six events in 2007 are used to pinpoint the shot times to < 1 second. Variations in the acoustic branches and signal arrival times at the arrays are used to probe variations in atmospheric structure. Although we currently use coupled signals we anticipate studying dense acoustic network recordings as the USArray is currently being upgraded with infrasound microphones. These new sensors will allow us to make semi-continental scale network recordings of infrasound signals free of concerns about how the signals observed on seismic channels were modified when being coupled to seismic.

  1. 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

  2. Topographic effects on infrasound propagation.

    PubMed

    McKenna, Mihan H; Gibson, Robert G; Walker, Bob E; McKenna, Jason; Winslow, Nathan W; Kofford, Aaron S

    2012-01-01

    Infrasound data were collected using portable arrays in a region of variable terrain elevation to quantify the effects of topography on observed signal amplitude and waveform features at distances less than 25 km from partially contained explosive sources during the Frozen Rock Experiment (FRE) in 2006. Observed infrasound signals varied in amplitude and waveform complexity, indicating propagation effects that are due in part to repeated local maxima and minima in the topography on the scale of the dominant wavelengths of the observed data. Numerical simulations using an empirically derived pressure source function combining published FRE accelerometer data and historical data from Project ESSEX, a time-domain parabolic equation model that accounted for local terrain elevation through terrain-masking, and local meteorological atmospheric profiles were able to explain some but not all of the observed signal features. Specifically, the simulations matched the timing of the observed infrasound signals but underestimated the waveform amplitude observed behind terrain features, suggesting complex scattering and absorption of energy associated with variable topography influences infrasonic energy more than previously observed. PMID:22280569

  3. 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).

  4. 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.

  5. Effect of time-varying tropospheric models on near-regional and regional infrasound propagation as constrained by observational data

    NASA Astrophysics Data System (ADS)

    McKenna, Mihan H.; Stump, Brian W.; Hayward, Chris

    2008-06-01

    The Chulwon Seismo-Acoustic Array (CHNAR) is a regional seismo-acoustic array with co-located seismometers and infrasound microphones on the Korean peninsula. Data from forty-two days over the course of a year between October 1999 and August 2000 were analyzed; 2052 infrasound-only arrivals and 23 seismo-acoustic arrivals were observed over the six week study period. A majority of the signals occur during local working hours, hour 0 to hour 9 UT and appear to be the result of cultural activity located within a 250 km radius. Atmospheric modeling is presented for four sample days during the study period, one in each of November, February, April, and August. Local meteorological data sampled at six hour intervals is needed to accurately model the observed arrivals and this data produced highly temporally variable thermal ducts that propagated infrasound signals within 250 km, matching the temporal variation in the observed arrivals. These ducts change dramatically on the order of hours, and meteorological data from the appropriate sampled time frame was necessary to interpret the observed arrivals.

  6. 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

  7. Probing the atmosphere with infrasound

    NASA Technical Reports Server (NTRS)

    Posmentier, E. S.; Donn, W. L.

    1969-01-01

    Recent studies are reported which have contributed to the knowledge of atmospheric structure and have established the practicality of infrasonic techniques for probing the atmosphere to heights of 120 km or more. Observations of a few types of infrasound are reviewed, and the theories used to account for the infrasound propagation and the deduced atmospheric structures are discussed.

  8. 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

  9. Infrasound Rocket Signatures

    NASA Astrophysics Data System (ADS)

    Olson, J.

    2012-09-01

    This presentation reviews the work performed by our research group at the Geophysical Institute as we have applied the tools of infrasound research to rocket studies. This report represents one aspect of the effort associated with work done for the National Consortium for MASINT Research (NCMR) program operated by the National MASINT Office (NMO) of the Defense Intelligence Agency (DIA). Infrasound, the study of acoustic signals and their propagation in a frequency band below 15 Hz, enables an investigator to collect and diagnose acoustic signals from distant sources. Absorption of acoustic energy in the atmosphere decreases as the frequency is reduced. In the infrasound band signals can propagate hundreds and thousands of kilometers with little degradation. We will present an overview of signatures from rockets ranging from small sounding rockets such as the Black Brandt and Orion series to larger rockets such as Delta 2,4 and Atlas V. Analysis of the ignition transients provides information that can uniquely identify the motor type. After the rocket ascends infrasound signals can be used to characterize the rocket and identify the various events that take place along a trajectory such as staging and maneuvering. We have also collected information on atmospheric shocks and sonic booms from the passage of supersonic vehicles such as the shuttle. This review is intended to show the richness of the unique signal set that occurs in the low-frequency infrasound band.

  10. The Numerical Simulation of Infrasound Generated by Convective Storms

    NASA Astrophysics Data System (ADS)

    Schecter, D.; Nicholls, M. E.

    2009-12-01

    Recent observations and theoretical considerations suggest that a developing tornado has a detectable signature in the infrasound of a severe weather system [A.J. Bedard Jr., Mon. Weather Rev., 133, 241 (2005)]. In order to reliably distinguish the vortex signal from extraneous noise, it is essential to advance current understanding of the various mechanisms that produce infrasound in atmospheric convection. Without detailed observations of the acoustic sources within a storm, numerical modeling may be the best method of investigation. Here, we consider the feasibility of using a special version of the Regional Atmospheric Modeling System (RAMS) that is customized to simulate aeroacoustics. Comparison to analytical results demonstrates that the customized model adequately generates the infrasound of tornado-like vortices, and of basic diabatic cloud processes. Sensitivity to the microphysics parameterization is briefly addressed. Provisional simulations suggest that a moderate-to-strong tornado can adiabatically generate infrasound of much greater intensity than the infrasound of a generic hail-producing thunderstorm, in the 0.1-3 Hz frequency range [D.A. Schecter et al., J. Atmos. Sci., 65, 685 (2008)]. More detailed numerical studies are underway to verify this conclusion, and to further understand the production of infrasound in a broad spectrum of convective systems, ranging from non-precipitating cumuli to tornadic thunderstorms.

  11. Infrasound research in Spitsbergen

    NASA Astrophysics Data System (ADS)

    Vinogradov, Yuri; Kremenetskaya, Elena

    2013-04-01

    KB GS RAS has a good experience of joint registration of seismic and infrasound events, their detection and classification. Since 1999 the observations at the seismic and infrasound array "Apatity" are carried out. The array is located in the center of Kola Peninsula. Since 2009 we also have started infrasound observations in Spitsbergen Archipelago. Until then we have assumed that such measurements are not informative because of extremely strong winds there. However, after noise level measurements at three points (Barentsburg, Pyramiden and Ny-Byen) it was found that registration of infrasound signals is possible at an average level of wind noise. In November, 2010 an infrasound array has been installed near the seismic station BRBB. The stations are located 4 km far from the settlement of Barentsburg to reduce man-made noise. The infrasound array consists of 3 low-frequency microphones. Each microphone is installed with a wind-reducing filter. It was supposed that the infrasound array will record signals from cleaving glaciers while the seismic station will register signals caused by glaciers movements. 132 glaciers are situated in the central and northern part of Spitsbergen, more than 90 of them are surging. Observation of seismicity of the continental part of the Archipelago has revealed a seasonal periodicity of weak seismic events. Maximal numbers of weak seismic events are registered during Septembers and Octobers. One of possible explanations of the periodicity could be seasonal changes of glaciers activity. It is known that ice breaks cause sharp sounds. Registration of these acoustic waves and their comparison with seismic signals also was the primary goal of our research. Two nearest surging glaciers, Esmark and Nansen, are located to the north and north-east from the stations at distances 20 and 24 kilometers respectively. These glaciers are rather small but a lot of seismic events has been registered in their areas in 2007 and in 2010. Single events

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. Infrasound and Seismic Observation of the Hayabusa Reentry: Burst Signals and Air-to-Ground Coupling Process

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Hiramatsu, Y.; Yamamoto, M.; Furumoto, M.; Fujita, K.

    2012-12-01

    The Hayabusa, the world's first sample-return minor body explorer, reentered the Earth's atmosphere on June 13, 2010. This was the third direct reentry event from the interplanetary transfer orbit to the Earth at a velocity of over 11.2 km/s, and was the world's first case of a direct reentry of the spacecraft itself from the interplanetary transfer orbit. This was the very good and rare opportunity to study bolide class meteor phenomena by various aspects. Multi-site ground observations of the Hayabusa reentry were carried out in the Woomera Prohibited Area, Australia (Fujita et al., 2011). The observations were configured with optical imaging, spectroscopies, and shockwave detection with infrasound and seismic sensors. At three main stations (GOS2, GOS2A, and GOS2B), we installed small aperture infrasound/seismic arrays, as well as three single component seismic sub stations (GOS2B-sub1, to GOS2B-sub3) (Yamamoto et al., 2011; Ishihara et al., 2012). The infrasound and seismic sensors clearly recorded sonic-boom-type shockwaves from the Hayabusa sample return capsule (Ishihara et al., 2012). In addition, following capsule signal, lots of signals that probably correspond shockwave from disrupted fragments of spacecraft and energetic bursts of the spacecraft were also recorded (Yamamoto et al., 2011). In this study, we analyze signals generated by hypersonic motion of the disrupted fragments and energetic burst of the spacecraft. In addition, we examine the air-to-ground coupling process by comparing the waveforms computed by finite difference scheme with the actual ones. At all three arrayed main stations, after the capsule's shockwave arrival, we detect multiple shockwave signals by both infrasound and seismic sensors. For some of these signals arrive within 10 seconds after capsule's signal, we can identify one to one correspondence with optically tracked disrupted fragments of the spacecraft. Far after the capsule's signal, we also detect some arrivals of wave

  18. Health effects from low-frequency noise and infrasound in the general population: Is it time to listen? A systematic review of observational studies.

    PubMed

    Baliatsas, Christos; van Kamp, Irene; van Poll, Ric; Yzermans, Joris

    2016-07-01

    A systematic review of observational studies was conducted to assess the association between everyday life low-frequency noise (LFN) components, including infrasound and health effects in the general population. Literature databases Pubmed, Embase and PsycInfo and additional bibliographic sources such as reference sections of key publications and journal databases were searched for peer-reviewed studies published from 2000 to 2015. Seven studies met the inclusion criteria. Most of them examined subjective annoyance as primary outcome. The adequacy of provided information in the included papers and methodological quality of studies was also addressed. Moreover, studies were screened for meta-analysis eligibility. Some associations were observed between exposure to LFN and annoyance, sleep-related problems, concentration difficulties and headache in the adult population living in the vicinity of a range of LFN sources. However, evidence, especially in relation to chronic medical conditions, was very limited. The estimated pooled prevalence of high subjective annoyance attributed to LFN was about 10%. Epidemiological research on LFN and health effects is scarce and suffers from methodological shortcomings. Low frequency noise in the everyday environment constitutes an issue that requires more research attention, particularly for people living in the vicinity of relevant sources. PMID:26994804

  19. 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.

  20. IDC Infrasound Pipeline initiative for technology development

    NASA Astrophysics Data System (ADS)

    Mialle, Pierrick; Le Bras, Ronan; Sudakov, Alexander; Fernando, Chaminda; Tomuta, Elena

    2015-04-01

    The first atmospheric event built exclusively 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 natural sources such as volcanic eruptions, earthquakes, microbaroms, meteorites entering the atmosphere and anthropogenic sources such as mining and accidental explosions. The IDC routinely processes infrasound data and creates automatic bulletins which are then reviewed interactively.. The IDC advances its methods and continuously improves its automatic systems, including 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. The current operational system handles seismic, hydroacoustic, and infrasound technologies within the same instance of the Global Association (GA) automatic association algorithm. The Infrasound Pipeline initiative consists in separating the infrasound technology at the stage of automatic association. An objective of this study is to reduce the number of automatically associated infrasound arrivals that are rejected by the analysts. This study also prepares the way for the implementation of the next generation of automatic waveform association algorithms. Infrasound processing in Global Association (GA) is revisited to pursue a lower ratio of false alarms. Tests are performed using historical events from IDC bulletins and the Infrasound Reference Event Data Base (IRED).

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  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. 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.

  10. 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.

  11. 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.

  12. 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

  13. USArray recordings of infrasound generated by the Chelyabinsk Meteor and other, smaller bolides

    NASA Astrophysics Data System (ADS)

    de Groot-Hedlin, Catherine; Hedlin, Michael

    2014-05-01

    A small asteroid that entered Earth's atmosphere near the city of Chelyabinsk, Russia, generated infrasound signals that were recorded by USArray barometers at distances from 6000-10000 km from the source. The infrasound recordings made of this event by these arrays are unprecedented, due to rarity of this type of event and the high density and spatial extent of the recording network. Signal characteristics vary across the network; infrasound arrivals recorded in Alaska and along the U.S. northwest coast had higher velocities and higher frequency content than those recorded in the eastern part of the network. The recorded pressure amplitudes at Alaska sites were significantly larger than for the remaining stations. Atmospheric specifications of global wind and sound speeds indicate the presence of a stratospheric duct for propagation to Alaska and stations along the northwest coast; however, most USarray stations lie within a thermospheric duct. Raytrace modeling confirms that, at stations in Alaska and the northwest U.S., the arrival times and durations of stratospherically ducted rays are consistent with observed arrivals at frequencies above the microbarom band. At lower frequencies, arrival times are consistent with thermospheric ducting at stations across the network. Estimates of infrasound attenuation from the Chelyabisk meteor to the recording sites were made using an attenuation formula derived from parabolic equation simulations. The results suggest that, under the assumption that infrasound was radiated isotropically from the Chelyabinsk meteor, thermospheric returns have higher than expected amplitudes as compared to stratospheric returns at the same frequencies. We examine in greater detail our assumption of isotropic infrasound radiation from a bolide explosion using a number of much smaller fireball events observed at seismic and infrasound sensors at the USArray.

  14. 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

  15. Airborne infrasound: A new way to explore the 3D acoustic wavefield

    NASA Astrophysics Data System (ADS)

    Jones, K. R.

    2015-12-01

    As a part of the Source Physics Experiment (SPE) site characterization and explosive test series, we developed and deployed an airborne octocopter infrasound platform. Traditionally, infrasound data is collected with sensors and arrays that are installed on the ground. For most applications this is sufficient but can be limiting when observing non-isotropic sources, such as underground explosions, at close range. To develop and test the airborne infrasound platform we recorded data from a seismo-acoustic hammer source at the Nevada National Security Site (NNSS). During early field-testing of the hammer source we found that, as the 13 metric ton mass hit the ground, a significant downward deflection of the surrounding surface imparted an observable infrasound pressure wave into the atmosphere. We compared waveforms collected at various vertical and horizontal offsets from the hammer source and found that the peak frequencies differed when observed directly above the source compared to the horizontal offsets. 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.

  16. IDC Infrasound Pipeline development

    NASA Astrophysics Data System (ADS)

    Mialle, P.; Bittner, P.; Brown, D.; Given, J.

    2012-04-01

    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, 44 infrasound stations from the International Monitoring System (IMS) have been installed and are transmitting data to the IDC. The growing amount of infrasound data and detections produced by the automatic system challenged the station and network processing at the IDC, which require the Organization to improve the infrasound data processing. For nearly 2 years, the IDC resumed automatic processing of infrasound data reviewed by interactive analysis; the detected and located events are being systematically included in the Late Event Bulletin (LEB) and REB. Approximately 16% of SEL3 (Selected Event List 3, produced 6 hours after real-time) events with an infrasound component make it to the IDC bulletins and 41% of SEL3 events rejected after review are built including only 2 associated infrasound phases (and potentially seismic and hydroacoustic detections). Therefore, the process whereby infrasound and seismic detections are associated into an event needed to be investigated further. The IDC works on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold. Thus the IDC investigates ways to refine the signal characterization methodology and the association criteria. The objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the SEL3 pipeline when generating the LEB and REB bulletins. The study is performed in the virtual Data Exploitation Center (vDEC) from the CTBTO in order to separate the automatic processing into two streams: seismic and hydroacoustic (SH) pipeline on one side, and infrasound (I) pipeline on the other side. The "fusion" of the two parallel event-forming streams will have to be

  17. Infrasound from the Chelyabinsk Meteor recorded at the USArray

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    A small asteroid that entered Earth's atmosphere near the city of Chelyabinsk, Russia, generated infrasound signals that were recorded by USArray barometers at distances from 6000-10000 km from the source. The infrasound recordings made of this event by these arrays are unprecedented, due to the high density of the networks and their spatial extent. Signal characteristics vary across the network; infrasound arrivals recorded in Alaska and along the U.S. northwest coast had higher velocities and higher frequency content than those recorded in the eastern part of the network. Waveform amplitudes at Alaska sites were approximately ten times larger than for the remaining stations, much more than expected due solely to their shorter travel paths. Atmospheric specifications of global wind and sound speeds indicate the presence of a stratospheric duct for propagation to Alaska and stations along the northwest coast; however, most USarray stations lie within a thermospheric duct. Raytrace modeling confirms that, at stations in Alaska and the northwest U.S., the arrival times and durations of stratospherically ducted rays are consistent with observed arrivals at frequencies above the microbarom band. At lower frequencies, arrival times are consistent with thermospheric ducting at stations across the network. An attenuation formula derived from parabolic equation simulations is used to estimate infrasound transmission losses at all USArray stations, using simplified models of the effective sound speed along each source-receiver path. Results indicate that, under the assumption of an isotropic source, attenuation estimates for most USArray sites are in agreement with observed variations in waveform amplitudes. However, stations in the northwest U.S, which lie along a geographic boundary between stratospheric and thermospheric ducting, have lower than expected amplitudes.

  18. Charting a Course for the Infrasound Renaissance

    NASA Astrophysics Data System (ADS)

    Garces, M.; Bass, H.; Hedlin, M.; Hayward, C.; Bowman, R.; Brown, D.; Businger, S.; Butler, R.; Chouet, B.; Drob, D.; Hetzer, C.; Koyanagi, S.; Mattioli, G.; McCormack, D.; Merrifield, M.; Pack, D.; Swanson, D.; Veith, K.; Voight, B.; Willis, M.

    2003-12-01

    The turn of the 21st century marks the onset of a renaissance in the field of infrasound, which had been dormant for ~30 years. The ongoing deployment of a global infrasound network has reawakened the field to a world of high-resolution digital array data, rapid communication, and seemingly unlimited growth in computing power. Complex phenomena that could only be addressed in general terms three decades ago can now be measured, analyzed, and modeled with unprecedented fidelity. Many fundamental problems in infrasound are now being revisited, and infrasonic observations are being integrated with other technologies (such as seismic, strainmeter and infrared) for the discovery of new phenomena or the refinement of geophysical studies. On July 24-25, 2003, the National Science Foundation sponsored a group of infrasound experts and interdisciplinary researchers to convene in Waikoloa, Hawaii, and chart a course for basic US infrasound research. The conveners selected key projects that would lead to significant advances in our understanding of infrasound generated by effusive and explosive volcanoes, ocean swells, bolides, fauna, severe weather, and long-period atmospheric instabilities. Projects were also proposed to refine our knowledge of atmospheric dynamics and transport mechanisms. A sampling of these projects is discussed in light of their contributions to our fundamental scientific understanding and their impact on the geophysical community.

  19. The Complementary Nature of Seismic and Infrasound Technologies in Regional Monitoring (Invited)

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Under current CTBTO event detection and location operating conditions, signal detection is a station-centric decision (was an event phase detected at this station?), rather than a global hypothesis test. Currently, infrasound and seismic detection use signal detectors run independently on each technology. It is only after event formation that the observations and inferences are merged. Development of this independent processing is a result of the vastly different signal and noise characteristics of these two waveform technologies. However, for specific signals there may be a utility to a joint seismic-infrasound detector. For example, noise estimates from one technology may help characterize or identify the noise on another technology (wind couples to both infrasound and seismic). Back-projection methods for both seismic and infrasound could easily be combined to produce a common seismo-acoustic detection and associated event location. The opportunity exists to integrate detection and location into a single multi-disciplinary approach. One such example is the ongoing infrasound detection and location procedure that utilizes an adaptive F-detector as input into the Bayesian Infrasonic Source Location (BISL, Modrak et al. 2010) procedure that provides an estimate of source location using assigned prior probabilities based on what is known of the propagation path and on the signal detector estimates (arrival time, phase velocity and azimuth). As the atmospheric model is better defined these priors may be changed, thus linking improved location estimates directly to improvements in atmospheric models. The final step following event location is identification. Seismic and infrasound observations and their interpretation for the recent set of North Korean nuclear explosions in 2006, 2009, and 2013 provide a motivation for multiple disciplinary approach to this step as well. Seismic analysis of these tests have documented that for existing parameterized source models

  20. 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

  1. 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.

  2. 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.

  3. Infrasound Propagation Modeling for Explosive Yield Estimation

    NASA Astrophysics Data System (ADS)

    Howard, J. E.; Golden, P.; Negraru, P.

    2013-12-01

    This study focuses on developing methods of estimating the size or yield of HE surface explosions from local and regional infrasound measurements in the southwestern United States. A munitions disposal facility near Mina, Nevada provides a repeating ground-truth source for this study, with charge weights ranging from 870 - 3800 lbs. Detonation logs and GPS synchronized videos were obtained for a sample of shots representing the full range of weights. These are used to calibrate a relationship between charge weight and spectral level from seismic waveforms recorded at the Nevada Seismic Array (NVAR) at a distance of 36 km. Origin times and yields for the remaining shots are inferred from the seismic recordings at NVAR. Infrasound arrivals from the detonations have been continuously recorded on three four-element, small aperture infrasound arrays since late 2009. NVIAR is collocated with NVAR at a range of approximately 36 km to the northeast. FALN and DNIAR are located at ranges of 154 km to the north, and 293 km to the southeast respectively. Travel times and amplitudes for stratospheric arrivals at DNIAR show strong seasonal variability with the largest amplitudes and celerities occurring during the winter months when the stratospheric winds are favorable. Stratospheric celerities for FNIAR to the north are more consistent as they are not strongly affected by the predominantly meridional stratospheric winds. Tropospheric arrivals at all three arrays show considerable variability that does not appear to be a seasonal effect. Naval Research Laboratory Ground to Space (NRL-G2S) Mesoscale models are used to specify the atmosphere along the propagation path for each detonation. Ray-tracing is performed for each source/receiver pair to identify events for which the models closely match the travel-time observations. This subset of events is used to establish preliminary wind correction formulas using wind values from the G2S profile for the entire propagation path. These

  4. 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.

  5. 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.

  6. Infrasound detection of the Chelyabinsk meteor at the USArray

    NASA Astrophysics Data System (ADS)

    de Groot-Hedlin, Catherine D.; Hedlin, Michael A. H.

    2014-09-01

    On February 15, 2013 a small asteroid entered Earth's atmosphere near Chelyabinsk, Russia. This extremely rare event was recorded by the 400-station USArray deployed in the continental United States and Alaska. These stations recorded infrasound signals from the event at distances from 6000 to 10 000 km across a sector spanning 55° that encompassed the North Pole. This dense, extensive network permitted a detailed study of long-range infrasound propagation and source characteristics. We observe long wavetrains at all stations (ranging to over 100 min) but clear variations in the character of the wavetrains across the network. Ray-tracing through a spatially and temporally varying atmospheric model indicates the source excited resonance in the thermospheric duct to all stations. Resonance was also excited in a persistent stratospheric duct between the source and stations in Alaska and along the west coast of the United States due to favorable winds at those azimuths, leading to higher group velocities and frequency content at these stations than those to the east. An attenuation formula derived from parabolic equation simulations is used to estimate infrasound transmission losses at all stations, using simplified models of the effective sound speed along each source-receiver path. Observed variations in signal energies from higher than expected at stations in the thermospheric duct in the eastern United States, to lower than expected in Alaska, at azimuths nearly orthogonal to the asteroid's Mach cone, lead us to conclude that (1) the source was dominantly isotropic and (2) the model overestimates attenuation in the thermospheric duct.

  7. 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

  8. ECMWF SSW forecast evaluation using infrasound

    NASA Astrophysics Data System (ADS)

    Smets, P. S. M.; Assink, J. D.; Le Pichon, A.; Evers, L. G.

    2016-05-01

    Accurate prediction of Sudden Stratospheric Warming (SSW) events is important for the performance of numerical weather prediction due to significant stratosphere-troposphere coupling. In this study, for the first time middle atmospheric numerical weather forecasts are evaluated using infrasound. A year of near-continuous infrasound from the volcano Mount Tolbachik (Kamchatka, Russian Federation) is compared with simulations using high-resolution deterministic forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF). For the entire time span the nowcast generally performs best, indicated by a higher continuity of the predicted wavefront characteristics with a minimal back azimuth difference. Best performance for all forecasts is obtained in summer. The difference between the infrasound observations and the predictions based on the forecasts is significantly larger during the 2013 SSW period for all forecasts. Simulations show that the SSW onset is better captured by the 10 day forecast while the recovery is better captured by the nowcast.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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. PMID:22894187

  17. 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.

  18. In search of discernible infrasound emitted by numerically simulated tornadoes

    NASA Astrophysics Data System (ADS)

    Schecter, David A.

    2012-09-01

    The comprehensive observational study of Bedard (2005) provisionally found that the infrasound of a tornado is discernible from the infrasound of generic cloud processes in a convective storm. This paper discusses an attempt to corroborate the reported observations of distinct tornado infrasound with numerical simulations. Specifically, this paper investigates the infrasound of an ordinary tornado in a numerical experiment with the Regional Atmospheric Modeling System, customized to simulate acoustic phenomena. The simulation has no explicit parameterization of microphysical cloud processes, but creates an unsteady tornado of moderate strength by constant thermal forcing in a rotational environment. Despite strong fluctuations in the lower corner flow and upper outflow regions, a surprisingly low level of infrasound is radiated by the vortex. Infrasonic pressure waves in the 0.1 Hz frequency regime are less intense than those which could be generated by core-scale vortex Rossby (VR) waves of modest amplitude in similar vortices. Higher frequency infrasound is at least an order of magnitude weaker than expected based on infrasonic observations of tornadic thunderstorms. Suppression of VR waves (and their infrasound) is explained by the gradual decay of axial vorticity with increasing radius from the center of the vortex core. Such non-Rankine wind-structure is known to enable the rapid damping of VR waves by inviscid mechanisms, including resonant wave-mean flow interaction and "spiral wind-up" of vorticity. Insignificant levels of higher frequency infrasound may be due to oversimplifications in the computational setup, such as the neglect of thermal fluctuations caused by phase transitions of moisture in vigorous cloud turbulence.

  19. Collective bubble oscillations as a component of surf infrasound.

    PubMed

    Park, Joseph; Garcés, Milton; Fee, David; Pawlak, Geno

    2008-05-01

    Plunging surf is a known generator of infrasound, though the mechanisms have not been clearly identified. A model based on collective bubble oscillations created by demise of the initially entrained air pocket is examined. Computed spectra are compared to infrasound data from the island of Kauai during periods of medium, large, and extreme surf. Model results suggest that bubble oscillations generated by plunging waves are plausible generators of infrasound, and that dynamic bubble plume evolution on a temporal scale comparable to the breaking wave period may contribute to the broad spectral lobe of dominant infrasonic energy observed in measured data. Application of an inverse model has potential to characterize breaking wave size distributions, energy, and temporal changes in seafloor morphology based on remotely sensed infrasound. PMID:18529169

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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

  7. Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system

    NASA Astrophysics Data System (ADS)

    Marchetti, E.; Ripepe, M.; Ulivieri, G.; Kogelnig, A.

    2015-11-01

    Avalanche risk management is strongly related to the ability to identify and timely report the occurrence of snow avalanches. Infrasound has been applied to avalanche research and monitoring for the last 20 years but it never turned into an operational tool to identify clear signals related to avalanches. We present here a method based on the analysis of infrasound signals recorded by a small aperture array in Ischgl (Austria), which provides a significant improvement to overcome this limit. The method is based on array-derived wave parameters, such as back azimuth and apparent velocity. The method defines threshold criteria for automatic avalanche identification by considering avalanches as a moving source of infrasound. We validate the efficiency of the automatic infrasound detection with continuous observations with Doppler radar and we show how the velocity of a snow avalanche in any given path around the array can be efficiently derived. Our results indicate that a proper infrasound array analysis allows a robust, real-time, remote detection of snow avalanches that is able to provide the number and the time of occurrence of snow avalanches occurring all around the array, which represent key information for a proper validation of avalanche forecast models and risk management in a given area.

  8. 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.

  9. Atmospheric infrasound from nonlinear wave interactions during Hurricanes Felicia and Neki of 2009

    NASA Astrophysics Data System (ADS)

    Stopa, Justin E.; Cheung, Kwok Fai; GarcéS, Milton A.; Badger, Nickles

    2012-12-01

    Monitoring stations around the globe routinely detect microbarom signals with a dominant frequency of ˜0.2 Hz from regions of marine storminess. International Monitoring System (IMS) infrasound array IS59 in Kailua-Kona, Hawaii recorded clear signals in close proximity of Hurricanes Felicia and Neki of 2009 for a first-hand investigation of the detailed source mechanism through a hindcast analysis. A spectral wave model describes the tropical cyclone and ambient sea states through a system of two-way nested grids with forcing from a blended data set of global, regional, and cyclonic winds. The computed wave conditions are validated with altimetry measurements and utilized in an acoustic model to estimate the intensity and spatial distribution of the microbarom source. The model results elucidate origins of infrasound signals from the tropical cyclone waves as well as their interactions with the ambient conditions consisting of swells, wind seas, and storm waves from nearby systems. The positive correlation between the IS59 observations and the theoretical microbarom estimates, and the saturation of recorded signals from high-energy sources support the use of infrasound signals for inference of tropical cyclone waves.

  10. 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.

  11. 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

  12. 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

  13. Assessing Infrasound Network Performance Using the Ambient Ocean Noise

    NASA Astrophysics Data System (ADS)

    Stopa, J. E.; Cheung, K.; Garces, M. A.; Williams, B.; Le Pichon, A.

    2013-12-01

    Infrasonic microbarom signals are attributed to the nonlinear resonant interaction of ocean surface waves. IMS stations around the globe routinely detect microbaroms with a dominant frequency of ~0.2 Hz from regions of marine storminess. We have produced the predicted global microbarom source field for 2000-2010 using the spectral wave model WAVEWATCH III in hindcast mode. The wave hindcast utilizes NCEP's Climate Forecast System Reanalysis (CFSR) winds to drive the ocean waves. CFSR is a coupled global modeling system created by a state-of-the-art numerical models and assimilation techniques to construct a homogenous dataset in time and space at 0.5° resolution. The microbarom source model of Waxler and Gilbert (2005) is implemented to estimate the ocean noise created by counter-propagating waves with similar wave frequencies. Comparisons between predicted and observed global microbarom fields suggest the model results are reasonable; however, further error analysis between the predicted and observed infrasound signals is required to quantitatively assess the predictions. The 11-year hindcast suggests global sources are stable in both magnitude and spatial distribution. These statistically stable features represent the ambient microbarom climatology of the ambient ocean noise. This supports the use of numerical forecast models to assess the IMS infrasound network performance and explosion detection capabilities in the 0.1-0.4 Hz frequency band above the ambient ocean noise. Theoretical/modeled microbarom source strength (colors) versus infrasonic observations from the IMS network (directional histograms). The contours represent the maximum intersections from the recorded acoustic signals for a large extra-tropical event on December 7, 2009.

  14. 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.

  15. Using infrasound to constrain ash plume height

    NASA Astrophysics Data System (ADS)

    Lamb, Oliver; De Angelis, Silvio; Lavallée, Yan

    2016-04-01

    Airborne volcanic ash advisories are currently based on analyses of satellite imagery with relatively low temporal resolution, and numerical simulations of atmospheric plume dispersion. These simulations rely on key input parameters such as the maximum height of eruption plumes and the mass eruption rate at the vent, which remain loosely constrained. In this study, we present a proof-of-concept workflow that incorporates the analysis of volcanic infrasound with numerical modelling of volcanic plume rise in a realistic atmosphere. We analyse acoustic infrasound records from two explosions during the 2009 eruption of Mt. Redoubt, USA, that produced plumes reaching heights of 12-14 km. We model the infrasonic radiation at the source under the assumptions of linear acoustic theory and calculate variations in mass ejection velocity at the vent. The estimated eruption velocities serve as the input for numerical models of plume rise. The encouraging results highlight the potential for infrasound measurements to be incorporated into numerical modelling of ash dispersion, and confirm their value for volcano monitoring operations.

  16. 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).

  17. Infrasound from the 2012-2013 Plosky Tolbachik, Kamchatka fissure eruption

    NASA Astrophysics Data System (ADS)

    Albert, Sarah; Fee, David; Firstov, Pavel; Makhmudov, Evgeniy; Izbekov, Pavel

    2015-12-01

    We use both regional and local infrasound data to investigate the dynamics of the 2012-2013 eruption of Tolbachik Volcano, Kamchatka, Russia during select periods of time. Analysis of regional data recorded at the IMS array IS44 in southern Kamchatka, ~ 384 km from the vent focuses on the eruption onset in November 2012, while analysis of local data focuses on activity in February and August 2013. Signals recorded from Tolbachik suggest a change in eruptive intensity possibly occurred from November 27-30, 2012. Local infrasound data recorded at distances of 100-950 m from the vent are characterized primarily by repeated, transient explosion signals indicative of gas slug bursts. Three methods are employed to pick slug burst events in February and August. The nature of slug bursts makes a monopole acoustic source model particularly fitting, permitting volume outflux and slug radius calculations for individual events. Volume outfluxes and slug radii distributions provide three possible explanations for the eruption style of Tolbachik Volcano from mid-February to late August. Cumulative outflux for slug bursts (i.e. mass of emissions from individual bursts) derived by infrasound for both February and August range from < 100 to ~ 3000 kg. These values are greater than infrasound-derived emissions calculated at Pacaya Volcano, but less than those calculated at Mt. Erebus Volcano. From this, we determine slug bursts at Tolbachik Volcano in February and August were larger on average than those at Pacaya Volcano in 2010, but smaller on average than those at Mt. Erebus in 2008. Our overall emissions estimates are in general agreement with estimates from satellite observations. This agreement supports the monopole source inversion as a potential method for estimating mass of emissions from slug burst events.

  18. Results of Infrasound Interferometry in Netherlands

    NASA Astrophysics Data System (ADS)

    Fricke, J. T.; Ruigrok, E. N.; Evers, L. G.; Simons, D. G.; Wapenaar, K.

    2012-04-01

    The travel time of infrasound through the atmosphere depends on the temperature and the wind. These atmospheric conditions could be estimated by measuring the travel times between different receivers (microbarometers). For such an estimation an inverse model of the propagation of infrasound through the atmosphere is essential. In the first step it is useful to build a forward model. The inputs of our raytracing model are the atmospheric conditions and the positions of source and receiver. The model consists of three elements the source, the channel and the receiver. The source is a blast wave or microbaroms. The channel is the atmosphere and it takes into account the travel time along the eigen ray, the attenuation of the different atmospheric layers, the spreading of the rays and the influence of caustics. Each receiver is reached by different rays (eigen rays). To determine the eigen rays is part of the receiver element. As output the model generates synthetic barograms. The synthetic barograms can be used to explain measured barograms. Furthermore the synthetic barograms can also be used to evaluate the determination of the travel time. The accurate travel time is for the inverse model as input essential. Since small changes of the travel time lead to big changes of the output (temperature and wind). The travel time between two receivers is determined by crosscorrelating the barograms of these two receivers. This technique was already successfully applied in the troposphere (Haney, 2009). We show that the same can be achieved with more complicated stratospheric phases. Now we compare the crosscorrelation of synthetic barograms with the crosscorrelation of measured barograms. These barograms are measured with the 'Large Aperture Infrasound Array' (LAIA). LAIA is being installed by the Royal Netherlands Meteorological Institute (KNMI) in the framework of the radio-astronomical 'Low Frequency Array' (LOFAR) initiative. LAIA will consist of thirty microbarometers

  19. Development and Application of First- and Second-Pass Clutter-Reduction Techniques for Nuclear Blast Detection at Infrasound Stations

    NASA Astrophysics Data System (ADS)

    Hetzer, C. H.; Waxler, R.

    2009-12-01

    The number of spurious arrivals observed at infrasound stations worldwide, often tens to hundreds per day per station, places great strain on human analysts tasked to eliminate arrivals of non-interest. Reliable automated arrival-classification systems are necessary for any effective real-time or near-real-time monitoring regime. We explore the utility and effectiveness of processor-based and physics-based techniques exploiting the strengths of the PMCC processor and the theoretical effects of propagation and attenuation on the spectra of explosive sources, both in terms of reducing the clutter volume at a continuously-operating research infrasound array in central Mississippi, and at preserving signals from known explosive sources recorded in Nevada. Possible fallacies in the assumptions underlying some common techniques will also be discussed.

  20. Deep infrasound radiated by the Sumatra earthquake and tsunami

    NASA Astrophysics Data System (ADS)

    Garcés, M.; Caron, P.; Hetzer, C.; Le Pichon, A.; Bass, H.; Drob, D.; Bhattacharyya, J.

    Infrasound arrays in the Pacific and Indian oceans that are part of the International Monitoring System (IMS) of the Comprehensive Nuclear Test Ban Treaty (CTBT) recorded distinct signatures associated with the 26 December 2004 Sumatra earthquake (M/9, http://earthquake.usgs.gov/) and tsunami. Although the radiation of infrasound from large continental earthquakes is established [e.g., Le Pichon et al., 2003], the results presented in the present article indicate that islands undergoing significant surface displacements from submarine earthquakes can produce infrasound.Far more intriguing is the possibility that the initiation and propagation of a tsunami may produce low-frequency sound near the source as well as along coastlines and basins. Since distant sound effectively propagates at ˜300 m/s and tsunamis propagate at ˜200 m/s, precursory sound could potentially be used as a discriminant for tsunami genesis.

  1. 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.

  2. A Tribute to Hank Bass: The Past, Present, and Future of US Infrasound Research

    NASA Astrophysics Data System (ADS)

    Garces, M.; Drob, D.; Golden, P.; Hedlin, M.; Szuberla, C.; Waxler, R.; Whitaker, R.

    2008-12-01

    The deployment of the International Monitoring System (IMS) global infrasound network at the turn of the 21st century inspired a renaissance in innovation, development, and application of infrasound technology. In the United States, Hank Bass (1944-2008) was responsible for defining and directing the scientific agenda. Under his leadership, US research teams in academia, industry, and government evaluated and developed the infrastructure to deploy, maintain, and make optimal use of infrasound arrays in the IMS and national networks. Case studies of national and international interest, such as the April 23, 2001 megabolide, the February 1, 2003 Columbia disaster, and the 2004 Sumatra earthquake and tsunami, integrated monitoring technologies and renewed the value of infrasound in covering observational gaps. Dramatic technological improvements have extended the use of infrasound to new natural hazard and national security applications, which will be discussed within the context of nuclear explosion monitoring.

  3. 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.

  4. 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

  5. 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.

  6. Cardiac peroxisome proliferator-activated receptor-γ expression is modulated by oxidative stress in acutely infrasound-exposed cardiomyocytes.

    PubMed

    Pei, Zhaohui; Meng, Rongsen; Zhuang, Zhiqiang; Zhao, Yiqiao; Liu, Fangpeng; Zhu, Miao-Zhang; Li, Ruiman

    2013-12-01

    The aim of the present study was to examine the effects of acute infrasound exposure on oxidative damage and investigate the underlying mechanisms in rat cardiomyocytes. Neonatal rat cardiomyocytes were cultured and exposed to infrasound for several days. In the study, the expression of CAT, GPx, SOD1, and SOD2 and their activities in rat cardiomyocytes in infrasound exposure groups were significantly decreased compared to those in the various time controls, along with significantly higher levels of O2 (-) and H2O2. Decreased cardiac cell viability was not observed in various time controls. A significant reduction in cardiac cell viability was observed in the infrasound group compared to the control, while significantly increased cardiac cell viability was observed in the infrasound exposure and rosiglitazone pretreatment group. Compared to the control, rosiglitazone significantly upregulated CAT, GPx, SOD1, and SOD2 expression and their activities in rat cardiomyocytes exposed to infrasound, while the levels of O2 (-) or H2O2 were significantly decreased. A potential link between a significant downregulation of PPAR-γ expression in rat cardiomyocytes in the infrasound group was compared to the control and infrasound-induced oxidative stress. These findings indicate that infrasound can induce oxidative damage in rat cardiomyocytes by inactivating PPAR-γ. PMID:23632742

  7. 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. PMID:20329823

  8. Acoustic multipole source model for volcanic explosions and inversion for source parameters

    NASA Astrophysics Data System (ADS)

    Kim, Keehoon; Lees, Jonathan M.; Ruiz, Mario

    2012-12-01

    Volcanic explosions are accompanied by strong acoustic pressure disturbances in the atmosphere. With a proper source model, these acoustic signals provide invaluable information about volcanic explosion dynamics. Far-field solutions to volcanic infrasound radiation have been derived above a rigid half-space boundary, and a simple inversion method was developed based on the half-space model. Acoustic monopole and dipole sources were estimated simultaneously from infrasound waveforms. Stability of the inversion procedure was assessed in terms of variances of source parameters, and the procedure was reliable with at least three stations around the infrasound source. Application of this method to infrasound observations recorded at Tungurahua volcano in Ecuador successfully produced a reasonable range of source parameters with acceptable variances. Observed strong directivity of infrasound radiation from explosions at Tungurahua are successfully explained by the directivity of a dipole source model. The resultant dipole axis, in turn, shows good agreement with the opening direction of the vent at Tungurahua, which is considered to be the origin of the dipole source. The method is general and can be utilized to study any monopole, dipole or combined sources generated by explosions.

  9. 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).

  10. 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.

  11. 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

  12. 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

  13. 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

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

    NASA Astrophysics Data System (ADS)

    Fee, D.; Waxler, R.; Drob, D.; Gitterman, Y.; Given, J.

    2012-04-01

    The establishment of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has stimulated infrasound research and development. However, as the network comes closer to completion there exists a lack of large, well-constrained sources to test the network and its capabilities. Also, significant uncertainties exist in long-range acoustic propagation due to a dynamic, difficult to characterize atmosphere, particularly the thermosphere. In 2009 and 2011 three large scale infrasound calibration experiments were performed in Europe, the Middle East, Africa, and Asia. The goal of the calibration experiments were to test the IMS infrasound network and validate atmospheric and propagation models with large, well-constrained infrasound sources. This presentation provides an overview of the calibration experiments, including deployment, atmospheric conditions during the experiments, explosion characterization, infrasonic signal detection and identification, and a discussion of the results and implications. Each calibration experiment consisted of singular surface detonation of explosives with nominal weights of 82, 10.24, and 102.08 tons on 26 August 2009, 24 January 2011, and 26 January 2011, respectively. These explosions were designed and conducted by the Geophysical Institute of Israel at Sayarim Military Range, Israel and produced significant infrasound detected by numerous permanent and temporary infrasound arrays in the region. The 2009 experiment was performed in the summer to take advantage of the westerly stratospheric winds. Infrasonic arrivals were detected by both IMS and temporary arrays deployed to the north and west of the source, including clear stratospheric arrivals and thermospheric arrivals with low celerities. The 2011 experiment was performed during the winter, when strong easterly stratospheric winds dominated in addition to a strong tropospheric jet (the jet stream). These wind jets allowed detection

  15. IDC Infrasound Pipeline initiative for technology development

    NASA Astrophysics Data System (ADS)

    Mialle, Pierrick; Bittner, Paulina; Brown, David; Given, Jeffrey

    2013-04-01

    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. The growing amount of infrasound data and detections produced by the automatic system challenged the station and network processing at the IDC, which require the Organization to continually improve the infrasound data processing. For 3 years, the IDC resumed automatic processing of infrasound data reviewed by interactive analysis; the detected and located events are being systematically included in the Late Event Bulletin (LEB) and REB. Approximately 16% of SEL3 (Selected Event List 3, produced 6 hours after real-time) events with an infrasound component make it to the IDC bulletins. 41% of SEL3 events rejected after review are built including only 2 associated infrasound phases (with the potential addition of seismic and hydroacoustic detections). Therefore, the process whereby infrasound and seismic detections are associated into an event needed to be investigated further. The IDC works on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold. Thus the IDC investigates ways to refine the signal characterization methodology and the association criteria. The objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the SEL3 pipeline when generating the LEB and REB bulletins. The study is twofold, the first part consist of improving the detection accuracy at the station processing stage in the IDC development area by enhancing the infrasound signal detector DFX-PMCC (Detection and Feature eXtraction - Progressive Multi-Channel Correlation) used at the IDC. The second part is

  16. 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.

  17. Comparing Volcano Infrasound and Aeroacoustics Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Ogden, D. E.; Matoza, R. S.; Fee, D.

    2012-12-01

    The production of acoustic noise by fluid flows has been studied experimentally within engineering aeroacoustics for over 50 years. These works aim to correlate flow properties and dynamics with the produced acoustic spectra (i.e., patterns of frequencies and amplitude). These correlations are used to design flow fields in man-made jet engines and other machines to reduce the production of harmful acoustic signals and resulting hearing loss. Many of the flow fields in these man-made systems are analogous to those in volcanic eruptions. We postulate that the acoustic signals generated by these flows are also analogous and the aeroacoustics experimental results provide a starting point for modeling the noise generated by volcanic flow fields. Application of empirical results from these experiments to volcanic flow fields is non-trivial. Volcanic eruptions involve complexities not present in man-made experiments including but not limited to multiphase flow, buoyancy forces, and non-uniform atmosphere. This work explores methods by which some of the empirical results from aeroacoustics experiments can be modified for application to volcanic eruptions. Results are compared with observations of volcano infrasound. Preliminary comparison to numerical simulations of volcano infrasound may also be presented.

  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. Upgrade of the Plostina infrasound array

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela; Ionescu, Constantin; Tataru, Stefan

    2014-05-01

    Plostina infrasound station (IPLOR) is a large aperture array deployed in the central part of Romania since 2009, by National Institute for Earth Physics (NIEP). The initial set-up consisted of 3 elements (IPH4, IPH5, IPH6); in 2010, a fourth element (IPH7) was added; during 2012, two more sensors were installed in IPH2 and IPH3 sites. All 6 elements are equipped with Chaparral Physics Model 25 sensors. Upgrading works are currently ongoing at IPLOR, aiming to enhance the station performance in terms of automatic signal detection and characterization in the routine processing using PMCC algorithm. The infrasound data quality is improved through station design optimization and installation of more efficient wind-noise reduction systems. Solutions adopted took in account the recommendations provided by the 2011 Expert Group Meeting for the design of IMS infrasound stations, as well as the knowledge acquired during the NIEP participation, as associated member, to the ARISE design study project. After upgrading the IPLOR station to a 6-element array, the analysis of the data shows a visibly enhancement of the detection capability by increasing the lower frequency resolution (below 0.5 Hz). The improved array response indicates reducing spatial aliasing of higher frequency signals and increasing the degree of signal correlation between array elements, which are observed in a better characterization of the signal in terms of back-azimuth and horizontal trace velocity. In September 2013, NIEP started the works to improve the wind-noise reduction conditions at IPLOR station. The pipes and air-inlets installed at IPH4 element were replaced, in order to eliminate the potential points of air leak. The porous hoses at IPH5, IPH6 and IPH7 sites were replaced with new rosette pipe array systems: 20-port rosette design at IPH5 and IPH6, and 19-port rosette design at IPH7. The two circular porous hoses located at the IPH2 and IPH3 sites are scheduled for replacing in 2014. The new

  20. 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

  1. Detecting and characterizing infrasound signals with optical fiber infrasound sensors

    NASA Astrophysics Data System (ADS)

    Walker, Kristoffer; Zumberge, Mark; Berger, Jonathan; Hedlin, Michael; Arrowsmith, Stephen

    2005-04-01

    Optical Fiber Infrasound Sensors (OFIS) are long compliant tubes wrapped with two optical fibers that interferometrically measure the differential pressure variation along the length of the tube. Because each sensor averages spatially along the length of the tube, the frequency response of the recorded pressure variation is a function of the orientation of the OFIS sensor relative to the back azimuth and incidence angle of the incoming wave. We have exploited this property to investigate the ability of various OFIS geometries to determine the back azimuth of infrasound signals. We have found that an OFIS comprised of two orthogonal 89-m-long arms having their centers separated by 63 m can resolve the back azimuth of most infrasound signals with a good signal-to-noise ratio. We find a good match between the back azimuths determined with our technique and those determined for the same signals recorded on the co-located pipe array I57US with the Progressive Multichannel Cross-Correlation technique. Based on these results and additional synthetic tests, we have built and are testing a larger OFIS with several arms that will be able to resolve signals from all directions and with small signal-to-noise ratios.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Miniaturization and Autonomous Deployment of the Optical Fiber Infrasound Sensor

    NASA Astrophysics Data System (ADS)

    DeWolf, S.; Walker, K. T.; Zumberge, M. A.

    2010-12-01

    A key difficulty in infrasound signal detection is the noise created by spatially incoherent turbulence that is usually present in wind. Increasing wind speeds correlate with increasing noise levels across the entire infrasound band. Spatial separation of sensors with array processing provides only limited signal-to-noise improvement. Mechanical wind filters, like rosette pipe arrays, also help to reduce wind noise, but the rosette infrasound response depends on the apparent speed and frequency of the signal that propagates across the ports as well as the rosette size. This response places an upper limit of about 70 m on the diameter of rosettes; larger rosettes, while better at wind noise reduction, attenuate important infrasound signals arriving from all directions. Optical fiber infrasound sensors (OFIS) are line microphones that instantaneously integrate pressure along their lengths with laser interferometry. We have developed and tested computationally efficient beamforming techniques that permit the rapid estimation of back azimuth using an array of OFIS arms as well as an array deconvolution technique that accurately stacks weighted versions of the recordings to obtain the infrasound signal. In this presentation we report on the major changes to our OFIS deployment strategies to accommodate a recent installment of a four element array in the Big Chico Creek Ecological Reserve, near Chico, CA. This includes significant improvement of the data acquisition and real-time digital signal processing systems, development of a robust and low-noise laser source, reduction of the power budget to that compatible with solar power, and data telemetry that enables each sensor to run autonomously. We also demonstrate that the sensitivity of the OFIS is linear over a wide range of pressures, which combined with the dynamic range of the digitizer, also makes the OFIS suitable for impulsive, near-field source studies. Using one of the aforementioned beamforming techniques, we

  7. 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.

  8. 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.

  9. Microseism and infrasound generation by cyclones.

    PubMed

    Bowen, Samuel P; Richard, Jacques C; Mancini, Jay D; Fessatidis, Vassilios; Crooker, Benjamin

    2003-05-01

    A two-dimensional cylindrical shear-flow wave theory for the generation of microseisms and infrasound by hurricanes and cyclones is developed as a linearized theory paralleling the seminal work by Longuet-Higgins which was limited to one-dimensional plane waves. Both theories are based on Bernoulli's principle. A little appreciated consequence of the Bernoulli principle is that surface gravity waves induce a time dependent pressure on the sea floor through a vertical column of water. A significant difference exists between microseisms detected at the bottom of each column and seismic signals radiated into the crust through coherence over a region of the sea floor. The dominant measured frequency of radiated microseisms is matched by this new theory for seismic data gathered at the Fordham Seismic Station both for a hurricane and a mid-latitude cyclone in 1998. Implications for Bernoulli's principle and this cylindrical stress flow theory on observations in the literature are also discussed. PMID:12765375

  10. 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. PMID:25920837

  11. Atmospheric Infrasound from Hurricanes Felicia and Neki of 2009

    NASA Astrophysics Data System (ADS)

    Stopa, J. E.; Cheung, K.; Garces, M. A.; Badger, N. B.

    2011-12-01

    Microbaroms are infrasound signals with a dominant frequency at 0.2 Hz. Monitoring stations around the globe continuously detected strong microbaroms across the ocean. Hurricanes Felicia and Neki were well recorded in 2009 at the International Monitoring System's IS59 array located in Kailua-Kona. A theoretical acoustic source model is utilized to estimate the intensity and spatial distribution of microbaroms produced by surface waves in the open ocean. The tropical cyclone sea state is created by utilizing a spectral ocean wave model and blended wind fields of different spatial scales that include the global winds from NCEP's final analysis, regional winds from University of Hawaii Meteorology Department's Weather and Forecasting model, and high resolution tropical cyclone winds from a parametric hurricane model. The computed wave data is validated with altimetry measurements. The strong correlation between the microbarom estimates and the IS59 measurements supports the potential use of infrasound signals for warning of hazardous wave conditions.

  12. Characterization of NCPA Infrasound Sensors

    NASA Astrophysics Data System (ADS)

    Hart, D. M.; Jones, K. R.; Sauter, A.

    2011-12-01

    By adding NCPA (National Center for Physical Acoustics) Infrasound sensors to the eastern-half of the Transportable Array, the scientific community has gained another powerful tool for studying natural processes. In an effort to characterize the sensors, including the effect of the wind filter and acoustical porting, researchers at Sandia National Labs (SNL) FACT Site and IRIS PASSCAL have performed a series of tests that resulted in good agreement with the NCPA-provided response (20mV/Pa +-10%, .007Hz high-pass corner frequency). Through independent testing and verification we have gained confidence in the sensor's linearity over the pressure range tested, a measure of power usage, and a measure of the dynamic range the sensors are capable of delivering, indicating the instruments can measure signals well below the Bowman (2005) Acoustic Low Noise Model up to 8Hz. Researchers at the SNL Fact site have the capabilities not only to test the NCPA sensor in an acoustic pressure chamber, but also to test the equivalent of the entire infrasound system used in the TA stations: NCPA sensor, tubing, and wind reduction design (a PVC filter buried in a bag of pumice stone). SNL tests with this fully-ported infrasound system characterize the full system response. We found that the tubing used to port the sensor to the external wind reduction device adds a measurable 15Hz resonance to the response and influences the high-frequency roll-off point. At PASSCAL, we have performed an acceptance test on more than 350 NCPA sensors, and in the process, have collected statistics on their relative gains. The standard deviation of the relative gain for all measured sensors is 5.32%. For 59 repeated tests of the two NCPA sensors used as references, the standard deviation is .15%, which suggests that acceptance testing can be used to constrain the gain of individual NCPA sensors much tighter than the population deviation.

  13. 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.

  14. 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).

  15. 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

  16. 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.

  17. 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

  18. 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. PMID:19206769

  19. Infrared observations of anonymous IRC sources

    NASA Technical Reports Server (NTRS)

    Strecker, D. W.; Ney, E. P.

    1974-01-01

    Infrared (0.9 to 18 microns) observations of 232 anonymous 2-micron Sky survey (IRC) sources are reported. Most of the objects appear to be late-type stars with little or no long-wave excess. About ten percent exhibit large excesses. Thirty-one of the brightest 11-micron sources have been remeasured to determine variability. These brighter objects appear to fall into two groups; one group resembles NML Tauri, while the other is like NML Cygni.

  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. Atmospheric Infrasound Propagation Modelling Using the Reflectivity Method

    NASA Astrophysics Data System (ADS)

    Näsholm, Sven Peter; Schweitzer, Johannes; Gibbons, Steven J.; Kvaerna, Tormod

    2015-04-01

    We demonstrate that the reflectivity method can be applied to the modelling of infrasound propagation. The reflectivity method is a slowness (or wavenumber) integration method widely applied in the seismological community to generate synthetic seismograms in layered media. The integrated function essentially describes the reflection coefficients between the layers. The method models P- and S-wave propagation and includes refractions and reflections, multiples, caustics, mode conversion, absorption and dispersion. Some limitations of conventional ray tracing are circumvented since head waves are represented and shadow zones are more correctly modelled. We apply a 2.5-D ray-tracing engine and a slightly modified version of Müller's reflectivity code to the atmospheric wind and temperature conditions at the time of the Drevja accidental explosion on December 17, 2013, in Northern Norway. The infrasound modelling results are compared with signals observed at the IS37 array station in Bardufoss, situated around 400 km north-east of the event. The effective sound speed approximation is applied, where the altitude-varying and range-independent sound speed is given by sum of the adiabatic sound speed and the wind projected in the horizontal propagation direction. An important observation is that an infrasound arrival, clearly observed in the IS37 data approximately 20 minutes after the explosion time, is predicted by the reflectivity method and not by ray-tracing, even for very densely sampled ray emission elevation angles. However at shorter ranges (~300 km), the corresponding phase is predicted by both modelling methods. There, the ray tracing shows this arrival as resulting from of a ray turning once in the stratosphere.

  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. ECMWF SSW forecast evaluation using infrasound

    NASA Astrophysics Data System (ADS)

    Smets, Pieter; Assink, Jelle; Le Pichon, Alexis; Evers, Läslo

    2016-04-01

    Accurate prediction of Sudden Stratospheric Warming (SSW) events is important for the performance of numerical weather prediction due to significant stratosphere--troposphere coupling. In this study, for the first time middle atmospheric numerical weather forecasts are evaluated using infrasound. A year of near continuous infrasound from Mt. Tolbachik (Kamchatka, Russian Federation) is compared with simulations using high resolution deterministic forecasts of the European Centre for Medium-range Weather Forecasts (ECMWF). For the entire timespan the nowcast generally performs best, indicated by a higher continuity and and smaller bearing difference. However, focussing on the period around the 2013 major SSW shows that while the SSW onset is better captured by the ten day forecast, the recovery is better captured by the nowcast. As such, this study demonstrates the use of infrasound in the evaluation of middle atmospheric weather forecasts and therefore its potential in the assessment of tropospheric forecast skill.

  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. The coherent field of infrasound - a global view with the IMS

    NASA Astrophysics Data System (ADS)

    Ceranna, Lars; Le Pichon, Alexis

    2016-04-01

    In this study we are going to present preliminary results of global coherent infrasound measured at IMS infrasound stations and its correlation with atmospheric dynamics. A new implementation of the Progressive Multi-Channel Correlation (PMCC) algorithm has been used, which enables a better characterization of all received signals in their wave parameter space (e.g., frequency-azimuth space, frequency-trace-velocity space). This, in-turn, allows an accurate signal discrimination, as well as source and propagation studies. For instance, we are using the processing for microbarom source and propagation studies and for analysing the occurrence of mountain associated waves. We are currently performing re-processing of the entire previous IMS infrasound database covering the time period from January 2003 to December 2015; whereas the number of stations has increased from 6 to 48. Results so far indicate a continuous spectrum of coherent signals at IMS stations within the 0.02 to 5.0 Hz band. Moreover, these results could be used for estimating network detection capability based on empirical station coherent infrasound noise models.

  6. 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. PMID:21376441

  7. 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

  8. 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.

  9. How to estimate yield using remote infrasound recordings?

    NASA Astrophysics Data System (ADS)

    Ceranna, L.; Le Pichon, A.

    2012-04-01

    Currently, estimates of radiated source energy or yield are based on empirical yield-scaling relations, which account for prevailing stratospheric winds. The most commonly used relation is derived from a high explosive dataset (Whitaker & Mutschlecner, 2008). However, limitations of this approach have been found by comparisons with reference events where problems arise either due to a fixed stratospheric wind speed or by an over-estimate of a known yield (e.g., Green et al., 2010). More realistic predictions can be achieved by using improved atmospheric specifications and measured station noise characteristics, as well as attenuation relations derived from operational propagation tools. An improved yield-scaling relation is considered (Le Pichon et al., 2012) which accounts for near-real time atmospheric up-dates and background noise calculations at various times of day for each month. This relation depends on a limited number of parameters describing the source (source altitudes between 0 and 30 km, dominant frequencies between 0.01 and 4.0 Hz) and the atmosphere (including naturally occurring gravity waves, altitude and strength of the stratospheric wind jet). All these parameters have a significant impact on infrasound propagation. We present a first approach for source energy (yield) estimates by combining all this information which provides a realistic picture of both station specific recording conditions and infrasound propagation from source to receiver. The spectrum of a full wave-train, whereas the local background noise is removed, can be inverted to a noise-free source spectrum at a certain reference distance, which is in turn related to certain yield based on empirical relations (e.g., Kinney & Graham, 1985). The capability of our approach is demonstrated for the two Sayarim explosion data-sets.

  10. 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.

  11. 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

  12. 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.

  13. 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. PMID:19045636

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Lyons, John J.; Haney, Matthew M.; Werner, Cynthia; Kelly, Peter; Patrick, Matthew; Kern, Christoph; Trusdell, Frank

    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.

  16. Infrasound increases intracellular calcium concentration and induces apoptosis in hippocampi of adult rats.

    PubMed

    Liu, Zhaohui; Gong, Li; Li, Xiaofang; Ye, Lin; Wang, Bin; Liu, Jing; Qiu, Jianyong; Jiao, Huiduo; Zhang, Wendong; Chen, Jingzao; Wang, Jiuping

    2012-01-01

    In the present study, we determined the effect of infrasonic exposure on apoptosis and intracellular free Ca²⁺ ([Ca²⁺]i) levels in the hippocampus of adult rats. Adult rats were randomly divided into the control and infrasound exposure groups. For infrasound treatment, animals received infrasonic exposure at 90 (8 Hz) or 130 dB (8 Hz) for 2 h per day. Hippocampi were dissected, and isolated hippocampal neurons were cultured. The [Ca²⁺]i levels in hippocampal neurons from adult rat brains were determined by Fluo-3/AM staining with a confocal microscope system on days 1, 7, 14, 21 and 28 following infrasonic exposure. Apoptosis was evaluated by Annexin V-FITC and propidium iodide double staining. Positive cells were sorted and analyzed by flow cytometry. Elevated [Ca²⁺]i levels were observed on days 14 and 21 after rats received daily treatment with 90 or 130 dB sound pressure level (SPL) infrasonic exposure (p<0.01 vs. control). The highest levels of [Ca²⁺]i were detected in the 130 dB SPL infrasonic exposure group. Meanwhile, apoptosis in hippocampal neurons was found to increase on day 7 following 90 dB SPL infrasound exposure, and significantly increased on day 14. Upon 130 dB infrasound treatment, apoptosis was first observed on day 14, whereas the number of apoptotic cells gradually decreased thereafter. Additionally, a marked correlation between cell apoptosis and [Ca²⁺]i levels was found on day 14 and 21 following daily treatment with 90 and 130 dB SPL, respectively. These results demonstrate that a period of infrasonic exposure induced apoptosis and upregulated [Ca²⁺]i levels in hippocampal neurons, suggesting that infrasound may cause damage to the central nervous system (CNS) through the Ca²⁺‑mediated apoptotic pathway in hippocampal neurons. PMID:21946944

  17. 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.

  18. Development of the IDC Infrasound Event Detection Pipeline

    NASA Astrophysics Data System (ADS)

    Mialle, P.; Bittner, P.; Brown, D.; Given, J. W.

    2012-12-01

    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 subsequent decade, 45 infrasound stations from the International Monitoring System (IMS) have been installed and are transmitting continuous data to the IDC. The growing amount of infrasound data and detections produced by the automatic system challenges the station and network processing at the IDC and requires the Organization to improve the infrasound data processing. In 2010, the IDC began full-time operational automatic processing of infrasound data followed by interactive analysis. The detected and located events are systematically included in the analyst-reviewed Late Event Bulletin (LEB) and REB. Approximately 16% of SEL3 (Selected Event List 3, automatically produced 6 hours after real-time) events with associated infrasound signals pass interactive analysis and make it to the IDC bulletins. 41% of those SEL3 events rejected after review have only 2 associated infrasound phases (and possibly other seismic and hydro-acoustic detections). Therefore, the process whereby infrasound detections are associated with events needs to be investigated further. The objective of this study is to reduce the number of associated infrasound arrivals that are falsely associated during the creation of the SEL3. There are two parts to the study. First, the detection accuracy at the infrasound arrays is improved by improving the infrasound signal detector, which is based on the PMCC (Progressive Multi-Channel Correlation) algorithm. The second part focuses on improving the reliability of the association algorithm. The association algorithm is enhanced to include better characterization of the variable atmospheric phenomena, which profoundly affect the detection patterns of the infrasound signals. The algorithm is then further tuned to reduce the

  19. Infrasound From Explosions: Large, Medium and Small

    NASA Astrophysics Data System (ADS)

    Whitaker, R. W.; Sandoval, T. D.; Mutschlecner, J. P.

    2003-12-01

    We will present analysis of infrasound signals of some recent high explosive (HE) events. The events include a recent explosive test, Watusi, at the Nevada Test Site (NTS) as well as some small explosions done under a Department of Defense (DOD) program, also at the NTS. Watusi, with a charge weight of 19 tons, was recorded at four Los Alamos National Laboratory/Department of Energy (LANL/DOE) infrasound arrays. Summary results will be presented, followed by a comparison to earlier HE data recorded by LANL arrays. These earlier data were from larger tests undertaken by the former Defense Nuclear Agency, now Defense Threat Reduction Agency. The Watusi data fit well with the earlier results for wind corrected amplitude versus scaled range. We also have recorded, from calendar year 2000 to the present, infrasound signals from 1000 to 2000 lb explosions executed at the NTS. These events were recorded at a range of 45 km by the LANL NTS array. These results show that detection at this range is fairly robust.

  20. 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.

  1. 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.

  2. Detection of infrasound and linear acceleration in fishes.

    PubMed Central

    Sand, O; Karlsen, H E

    2000-01-01

    Fishes have an acute sensitivity to extremely low-frequency linear acceleration, or infrasound, even down to below 1 Hz. The otolith organs are the sensory system responsible for this ability. The hydrodynamic noise generated by swimming fishes is mainly in the infrasound range, and may be important in courtship and prey predator interactions. Intense infrasound has a deterring effect on some species, and has a potential in acoustic barriers. We hypothesize that the pattern of ambient infrasound in the oceans may be used for orientation in migratory fishes, and that pelagic fishes may detect changes in the surface wave pattern associated with altered water depth and distant land formations. We suggest that the acute sensitivity to linear acceleration could be used for inertial guidance, and to detect the relative velocity of layered ocean currents. Sensitivity to infrasound may be a widespread ability among aquatic organisms, and has also been reported in cephalopods and crustaceans. PMID:11079418

  3. Infrasound sensitizes human glioblastoma cells to cisplatin-induced apoptosis.

    PubMed

    Rachlin, Kenneth; Moore, Dan H; Yount, Garret

    2013-11-01

    The development of nontoxic agents that can selectively enhance the cytotoxicity of chemotherapy is an important aim in oncology. This study evaluates the ability of infrasound exposure to sensitize glioblastoma cells to cisplatin-induced apoptosis. The infrasound was delivered using a device designed to replicate the unique infrasound emissions measured during external Qigong treatments. Human glioblastoma cell lines harboring wild-type p53 (U87) or mutant p53 (U251, SF210, and SF188) were treated in culture with cisplatin, infrasound emissions, or the combination of the 2 agents. Induction of apoptosis was quantified after 24 hours by flow cytometry following annexin V/propidium iodide staining. Infrasound emissions alone, delivered at moderate levels (~10 mPa) with dynamic frequency content (7-13 Hz), did not induce apoptosis, yet combining infrasound with cisplatin augmented the induction of apoptosis by cisplatin in all the 4 cell lines (P < .05). Increased cellular uptake of the fluorophore calcein associated with infrasound exposure was quantified by fluorescence microscopy as well as flow cytometry, demonstrating increased cell membrane permeability. The 4 cell lines differed in the degree to which infrasound exposure increased calcein uptake, and these differences were predictive of the extent to which infrasound enhanced cisplatin-induced apoptosis. When exposed to specific frequencies, membrane permeabilization also appeared to be differentially responsive for each cell line, suggesting the potential for selective targeting of tissue types using isolated infrasonic frequencies. Additionally, the pressure amplitudes used in this study were several orders of magnitude less than those used in similar studies involving ultrasound and shock waves. The results of this study provide support for using infrasound to enhance the chemotherapeutic effects of cisplatin in a clinical setting. PMID:23165942

  4. 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

  5. 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.

  6. 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.

  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. 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. 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

  10. Recording of remote ground explosions in the Barents Region by the Seismic &Infrasound Integrated Array "Apatity"

    NASA Astrophysics Data System (ADS)

    Vinogradov, Y.; Vinogradov, A.

    2003-04-01

    velocities (apparent velocities) range between 330-400 m/s, with the lowest values for the Iw phases and the highest values for the It phases. Seismic signals from the explosion were very low, and only P-waves were recorded. In contrary to the infrasound data the seismic ones were insufficient for a correct location of source, but allowed to determinate the origin time of explosion. We should note that a detection of infrasonic phases is very dependent on background atmospheric conditions, and that such phases are usually observed only during relatively quiet wind conditions. Our future plans include the installation of additional wind-noise-reducing pipe array to improve the delectability during windy conditions. After the projected infrasonic array in Karasjok, northern Norway, is installed, we plan to carry out joint processing of data from these two arrays in co-operation with NORSAR, Norway.

  11. Intense monotonic infrasound at Volcan Villarrica: Insights from an Integrated Seismo-acousto-optico-thermo-UV imager field approach

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Anderson, J.; Sanderson, R. W.; McIntosh, W. C.; Goto, A.; Waite, G. P.; Palma, J.; Richardson, J. P.

    2011-12-01

    Toward understanding the origin of the intense (>50 Pa RMS at crater rim) monotone tremor at Volcan Villarrica (Chile), we have deployed instrumentation, including cameras, suspended above the basaltic lava lake. In 2010 we observed a 65-m diameter spatter roof perforated by a 10 m-diameter vent (or skylight) providing a view into a 25 m-tall cavity and roiling lava lake beneath. Conjoint visual observations and infrasound modeling suggest that the 0.77 Hz infrasonic signal is a Helmholtz resonance phenomenon similar to that previously postulated for Kilauea and Shishaldin. A February-March 2011 field campaign was aimed at understanding the relation between surface activity and degassing and thermal flux by deploying a dense linear array of broadband seismo-acoustic sensors on the upper slopes of the volcano and within the upper crater. We also lowered time-synchronized cameras, pressure sensors, and thermocouples down into the vent. Against the background of intense infrasonic tremor we observed discrete strombolian eruptions and spattering events, which generate a preponderance of 5-10 Hz infrasound. A stable peaked infrasound monotone ranging from 0.65-0.8 Hz has been reported by our group and others at Villarrica in 2002, 2008, 2009, 2010, 2011. We propose that the conduit/vent geometry largely control the frequency content of the infrasound whereas the amplitude of the oscillation is controlled by gas emission rates, which we were able to quantify for SO2 in 2011 using UV absorption imagery.

  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. PMID:24116535

  13. 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.

  14. 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

  15. 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.

  16. Infrasonic Observations of the Final Flight of Space Shuttle Atlantis

    NASA Astrophysics Data System (ADS)

    Jones, K. R.; Hart, D. M.

    2011-12-01

    Infrasound arrivals from the July 2011 Space Shuttle Atlantis launch and re-entry were observed ~2,500 km away at Sandia's (SNL) Facility for Acceptance, Calibration and Testing (FACT) seven-element infrasound array. Space Shuttle Atlantis (STS-135) launched from the Kennedy Space Center (Florida) on July 8, 2011 for its final 14 day mission, culminating in a successful re-entry and landing on July 21, 2011. Infrasound from both the launch and the re-entry were clearly observed at the SNL FACT array due to the seasonal zonal wind reversals in the stratosphere and the quiet of early morning for the re-entry. In the northern hemisphere summer infrasound sources originating east of the array are observed more clearly than sources west of the array. While both the launch and re-entry were observed, the duration of detection, trace velocity, and correlation across the array varied. The launch was detected at the array for ~2 minutes while the re-entry was observed for a considerably greater amount of time, ~25 minutes. The launch of the shuttle produced less detectable infrasound because the trajectory carried the shuttle east, away from the array and disturbed the atmosphere to a lesser extent than at re-entry. During re-entry the shuttle passed much closer to the array, displaced more atmosphere, and generated infrasound for a longer period of time. The correlation across the array increased dramatically over background, peaking above 0.4 for the launch and over 0.9 for re-entry. In both cases the trace velocity stabilized between 0.35 and 0.38 km/s above background. Using FK processing we determined a back azimuth for the launch that correlated well to the location of the launch site at ~100°. Due to the higher, supersonic velocities of the shuttle and the atmospheric disturbance of re-entry, we were able to calculate several back azimuths over the duration of the observed signal. The back azimuths correlated very well with trajectory data provided by NASA and

  17. 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.

  18. Detection of Gravity Waves and Infrasound Signals at the USArray

    NASA Astrophysics Data System (ADS)

    de Groot-Hedlin, Catherine; Hedlin, Michael

    2015-04-01

    The USArray Transportable Array (TA) is a 400-station network that has been deployed in the continental United States since 2004. The network, which at its height spanned 2,000,000 km2, has gradually moved east across the country via station re-deployments. Although originally conceived as a seismic-only network, a suite of atmospheric pressure sensors added to each station starting in early 2010 allows for enhanced observations of pressure variations at the Earth's surface associated with infrasound and other atmospheric phenomena. We present novel techniques that make use of the close spacing of stations within the TA to detect and track the progress of pressure disturbances across the network. The method has been applied to the detection of both atmospheric gravity waves having periods from 40 minutes to 8 hours, and 1-3 Hz infrasound energy generated by meteoroids. The TA is sufficiently dense that gravity waves with wavelengths from tens to hundreds of kilometers are coherent between neighboring stations, but is too large for coherence across the entire network. To examine the characteristics of gravity waves propagating across the network, the TA is divided into a large number of elemental, triangular, sub-arrays consisting of three neighboring stations. Coherent analysis of the data at each triad provides a robust estimate of the signal's direction and speed. The results from all triads are combined to follow the progress of a gravity wave as it propagates across the TA. This method allows for observation of fine-scale variations in the speed, direction and amplitude of long period signals across the TA, as well as the statistics of these waves. The method has been applied to TA data collected over the eastern half of the continental United States over a 5-year timespan beginning on January 1, 2010. The network has detected particularly large and long-lived gravity waves such as from a tornadic storm system in the American south in April, 2011. In addition

  19. 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. PMID:27369137

  20. 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

  1. 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.

  2. 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

  3. Observe Z sources at High Mass Accretion Rates

    NASA Astrophysics Data System (ADS)

    Canizares, Claude

    2008-09-01

    We propose to test a new interpretation that links mass accretion rate to observed spectral changes in Z-sources in a diffwrent way than previously though. Integral part of the test is to catch Z-source on the horizontal branch (HB). There are a few sources where RXTE and previous observatories established a fairly accurate record of how often they appear on a specific spectral branch. 4 observations for 8 ks each has a 50% chance to observe GX 5-1 on the HB.

  4. 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.

  5. 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.

  6. Infrasound radiated by the Gerdec and Chelopechene explosions: propagation along unexpected paths

    NASA Astrophysics Data System (ADS)

    Green, David N.; Vergoz, Julien; Gibson, Robert; Le Pichon, Alexis; Ceranna, Lars

    2011-05-01

    Infrasound propagation paths through the atmosphere are controlled by the temporally and spatially varying sound speed and wind speed amplitudes. Because of the complexity of atmospheric acoustic propagation it is often difficult to reconcile observed infrasonic arrivals with the sound speed profiles predicted by meteorological specifications. This paper provides analyses of unexpected arrivals recorded in Europe and north Africa from two series of accidental munitions dump explosions, recorded at ranges greater than 1000 km: two explosions at Gerdec, Albania, on 2008 March 15 and four explosions at Chelopechene, Bulgaria, on 2008 July 3. The recorded signal characteristics include multiple pulsed arrivals, celerities between 0.24 and 0.34 km s-1 and some signal frequency content above 1 Hz. Often such characteristics are associated with waves that have propagated within a ground-to-stratosphere waveguide, although the observed celerities extend both above and below the conventional range for stratospheric arrivals. However, state-of-the-art meteorological specifications indicate that either weak, or no, ground-to-stratosphere waveguides are present along the source-to-receiver paths. By incorporating realistic gravity-wave induced horizontal velocity fluctuations into time-domain Parabolic Equation models the pulsed nature of the signals is simulated, and arrival times are predicted to within 30 s of the observed values (<1 per cent of the source-to-receiver transit time). Modelling amplitudes is highly dependent upon estimates of the unknown acoustic source strength (or equivalent chemical explosive yield). Current empirical explosive yield relationships, derived from infrasonic amplitude measurements from point-source chemical explosions, suggest that the equivalent chemical yield of the largest Gerdec explosion was of the order of 1 kt and the largest Chelopechene explosion was of the order of 100 t. When incorporating these assumed yields, the Parabolic

  7. Infrasound Generated by Strombolian Eruptions - Insights from Laboratory Experiments

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    In recent years infrasonic monitoring at volcanoes has become an increasingly common tool. Much of the current work on interpreting volcano infrasound has concentrated on Strombolian eruptions, and several mechanisms have been suggested for the sound produced at these eruptions. However, the precise mechanisms at the vent need to be identified and understood if infrasound recorded in the field is to be used to infer conditions in the volcanic system. In this work, laboratory experiments using audio recordings coupled with high speed video footage have been conducted to gain a deeper understanding of these sounds. A simplified analogue model is used as an analogy for a Strombolian eruption: an air bubble rises through a tank containing a viscous Newtonian liquid (golden syrup) and bursts at the surface. Although the experimental set-up is simple and idealized, it allows control of physical properties and measurement of the processes observed far more accurately than would be possible in the field. Physical parameters which may control the form of the acoustic wave produced, such as liquid viscosity (achieved by dilution of pure golden syrup with water) and bubble volume are investigated. Initial results show that the onset of the main part of the acoustic waveform occurs concurrently with the onset of bubble rupture. Trends in the amplitude and frequency of the acoustic waveform, as well as bubble rupture speed are seen as the liquid viscosity varied. A number of candidate mechanisms for the production of sound during the experiments have been investigated, and synthetic waveforms compared to experimental data. These include the flow of gas through a growing hole from a pressurised reservoir (the bubble), and the mass flux due to the collapse of the bubble film. Importantly it has been shown that even in this very simple case - the sound produced by the bursting of a hemispherical bubble formed at the surface of a viscous liquid - is not as simple as some theories

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Brief communication "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"

    NASA Astrophysics Data System (ADS)

    Schmitter, E. D.

    2010-02-01

    Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound but also modulate the charge density and the velocity field and in this way lead to electric and magnetic field oscillations in the 0.5-20-Hz range that can be monitored from a distance of several kilometers.

  13. 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.

  14. Detectability of Tengchong infrasound array in China

    NASA Astrophysics Data System (ADS)

    Su, Wei; Yuan, Songyong

    2016-04-01

    The Tengchong seismo-acoustic array located in southwest of China has been running for 5 years. We perform broadband (0.01-5 Hz) array processing with the infrasound continuous waveform data (from 1 January 2011 to 31 December 2015) using the Progressive Multi-Channel Correlation algorithm in 15 log-spaced frequency bands defined by Matoza et al.(2013).The detection results show microbaroms [0.1-0.5 Hz] come from azimuth between 180 and 240°during April to October related to the significant wave height in southern India ocean,but microbaroms come from azimuth between 30 and 90°during September to March related to the significant wave height in northern Pacific ocean. MAWs [0.01-0.1 Hz] come from azimuth between 270 and 360°,and between 90 and 160°. The detections with azimuth between 100 and 150° in December 2014 to January 2015 may be related to the several typhoons from the Western Pacific ocean. The PMCC results confirm that the coherent signals typically exhibit systematic seasonal variations.

  15. The importance of source positions during radio fine structure observations

    NASA Astrophysics Data System (ADS)

    Chernov, Guennadi P.; Yan, Yi-Hua; Fu, Qi-Jun

    2014-07-01

    The measurement of positions and sizes of radio sources in the observations of the fine structure of solar radio bursts is a determining factor for the selection of the radio emission mechanism. The identical parameters describing the radio sources for zebra structures (ZSs) and fiber bursts confirm there is a common mechanism for both structures. It is very important to measure the size of the source in the corona to determine if it is distributed along the height or if it is point-like. In both models of ZSs (the double plasma resonance (DPR) and the whistler model) the source must be distributed along the height, but by contrast to the stationary source in the DPR model, in the whistler model the source should be moving. Moreover, the direction of the space drift of the radio source must correlate with the frequency drift of stripes in the dynamic spectrum. Some models of ZSs require a local source, for example, the models based on the Bernstein modes, or on explosive instability. The selection of the radio emission mechanism for fast broadband pulsations with millisecond duration also depends on the parameters of their radio sources.

  16. 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.

  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. PMID:20649183

  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. Columbia/Einstein observations of galactic X-ray sources

    NASA Technical Reports Server (NTRS)

    Long, K. S.

    1979-01-01

    The imaging observations of galactic clusters are presented. These fall into three categories: pre-main-sequence stars in the Orion nebulae, isolated-main-and-post main-sequence stars, and supernova remnants SNR. In addition to SNR, approximately 30 sources were detected.

  1. 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.

  2. Location of space debris by infrasound

    NASA Astrophysics Data System (ADS)

    Asming, Vladimir; Vinogradov, Yuri

    2013-04-01

    After an exhausted stage has separated from a rocket it comes back to the dense atmosphere. It burns and divides into many pieces moving separately. Ballisticians can calculate an approximate trace of a falling stage and outline a supposed area where the debris can fall (target ellipse). Such ellipses are usually rather big in sizes (something like 60 x 100 km). For safety reasons all local inhabitants should be evacuated from a target area during rocket's launch. One of problems is that the ballistician can not compute the traces and areas exactly. There were many cases when debris had fallen outside the areas. Rescue teams must check such cases to make changes in rockets. The largest pieces can contain remains of toxic rocket fuel and therefore must be found and deactivated. That is why the problem of debris location is of significant importance for overland fall areas. It is more or less solved in Kazakhstan where large fragments of 1st stages can be seen in the Steppe but it is very difficult to find fragments of 2nd stages in Altai, Tomsk region and Komi republic (taiga, mountains, swamps). The rocket debris produces strong infrasonic shock waves during their reentry. Since 2009 the Kola Branch of Geophysical Survey of RAS participates in joint project with Khrunichev Space Center concerning with infrasound debris location. We have developed mobile infrasound arrays consisting of 3 microphones, analog-to-digit converter, GPS and notebook. The aperture is about 200 m, deployment time is less than 1 hour. Currently we have 4 such arrays, one of them is wireless and consists of 3 units comprising a microphone, GPS and radio-transmitter. We have made several field measurements by 3 or 4 such arrays placed around target ellipses of falling rocket stages in Kazakhstan ("Soyuz" rocket 1st stage), Altai and Tomsk region ("Proton" rocket 2nd stages). If was found that a typical 2nd stage divides into hundreds of pieces and each one generates a shock wave. This is a

  3. 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.

  4. 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.

  5. 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%.

  6. Epigallocatechin gallate (EGCG) attenuates infrasound-induced neuronal impairment by inhibiting microglia-mediated inflammation.

    PubMed

    Cai, Jing; Jing, Da; Shi, Ming; Liu, Yang; Lin, Tian; Xie, Zhen; Zhu, Yi; Zhao, Haibo; Shi, Xiaodan; Du, Fang; Zhao, Gang

    2014-07-01

    Infrasound, a kind of common environmental noise and a major contributor of vibroacoustic disease, can induce the central nervous system (CNS) damage. However, no relevant anti-infrasound drugs have been reported yet. Our recent studies have shown that infrasound resulted in excessive microglial activation rapidly and sequential inflammation, revealing a potential role of microglia in infrasound-induced CNS damage. Epigallocatechin gallate (EGCG), a major bioactive component in green tea, has the capacity of protecting against various neurodegenerative diseases via an anti-inflammatory mechanism. However, it is still unknown to date whether EGCG acts on infrasound-induced microglial activation and neuronal damage. We showed that, after 1-, 2- or 5-day exposure of rats to 16 Hz, 130 dB infrasound (2 h/day), EGCG significantly inhibited infrasound-induced microglial activation in rat hippocampal region, evidenced by reduced expressions of Iba-1 (a marker for microglia) and proinflammatory cytokines (IL-1β, IL-6, IL-18 and TNF-α). Moreover, infrasound-induced neuronal apoptosis in rat hippocampi was significantly suppressed by EGCG. EGCG also inhibited infrasound-induced activation of primary microglia in vitro and decreased the levels of proinflammatory cytokines in the supernatants of microglial culture, which were toxic to cultured neurons. Furthermore, EGCG attenuated infrasound-induced increases in nuclear NF-κB p65 and phosphorylated IκBα, and ameliorated infrasound-induced decrease in IκB in microglia. Therefore, our study provides the first evidence that EGCG acts against infrasound-induced neuronal impairment by inhibiting microglia-mediated inflammation through a potential NF-κB pathway-related mechanism, suggesting that EGCG can be used as a promising drug for the treatment of infrasound-induced CNS damage. PMID:24746834

  7. The source of Jovian auroral hiss observed by Voyager 1

    NASA Technical Reports Server (NTRS)

    Morgan, D. D.; Gurnett, D. A.; Kurth, W. S.; Bagenal, F.

    1994-01-01

    Observations of auroral hiss obtained from the Voyager 1 encounter with Jupiter have been reanalyzed. The Jovian auroral hiss was observed near the inner boundary of the warm Io torus and has a low-frequency cutoff caused by propagation near the resonance cone. A simple ray tracing procedure using an offset tilted dipole of the Jovian magnetic field is used to determine possible source locations. The results obtained are consistent with two sources located symmetrically with respect to the centrifugal equator along an L shell (L approximately = 5.59) that is coincident with the boundary between the hot and cold regions of the Io torus and is located just inward of the ribbon feature observed from Earth. The distance of the sources from the centrifugal equator is approximately 0.58 +/- 0.01 R(sub J). Based on the similarity to terrestrial auroral hiss, the Jovian is auroral hiss is believed to be generated by beams of low energy (approximately tens to thousands of eV) electrons. The low-frequency cutoff of the auroral hiss suggests that the electrons are accelerated near the inferred source region, possibly by parallel electric fields similar to those existing in the terrestrial auroral regions. A field-aligned current is inferred to exist at L shells just inward of the plasma ribbon. A possible mechanism for driving this current is discussed.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Chandra Orion Ultradeep Project: Observations and Source Lists

    NASA Astrophysics Data System (ADS)

    Getman, K. V.; Flaccomio, E.; Broos, P. S.; Feigelson, E. D.; Grosso, N.; Tsujimoto, M.; COUP Collaboration

    2004-08-01

    We present the observations, data analysis methodology, and tabulated results from the Chandra Orion Ultradeep Project (COUP). COUP is based on a single nearly-continuous 850 ks pointing towards the Orion Nebula obtained in January 2003. Over 1600 young stars are detected. Data preparation includes correction for charge transfer inefficiency and subpixel event repositioning. Source detection is based on two wavelet-based search algorithms optimized for maximum reduction of background. For each source, we perform data extraction, pileup correction, spectral and variability analysis, and broad-band luminosity determinations using the sophisticated semi-automated IDL-based ACIS Extract (AE) package. Our treatment of photon pileup using annular extraction regions is effective for both lightly and heavily piledup sources. The AE data products efficiently provide detailed and comprehensive information for point sources in ACIS fields. COUP is supported by Chandra grant SAO GO3-4009A (Feigelson PI). ACIS Extract is available at http://www.astro.psu.edu/xray/docs/TARA/ae_users_guide.html.

  16. 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

  17. 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

  18. Near-source and Remote Observations of Kilometric Continuum Radiation from Multispacecraft Observations

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Anderson, R. R.; Pickett, J. S.; Gurnett, D. A.; Matsumoto, H.

    2003-01-01

    [I] Kilometric continuum (KC) radiation was first identified from Geotail plasma wave observations. Past authors have shown that this emission has a frequency range that overlaps that of the auroral kilometric radiation (AKR) but is characterized by a fine structure of narrow-bandwidth, linear features that have nearly constant or drifting frequency. This fine structure is distinct from that of AKR. KC also apparently has a distinct source region probably associated with the low-latitude inner magnetosphere, consistent with direction-finding and ray-tracing results. We present new high-resolution electric and magnetic field observations of KC obtained by the Polar plasma wave instrument in the near-source region. These observations show intense electrostatic and less intense electromagnetic emissions near the magnetic equator at the plasmapause. Simultaneously, Geotail, located at 20 to 30 RE in radial distance, observes KC in the same frequency range. These data support a possible mode-conversion source mechanism near a region of high-density gradient. High-resolution data obtained from wideband receivers on board both Polar and Cluster show closely spaced bands of emission near the magnetic equator that may be due to many nearby independent sources of EM emission perhaps associated with density fluctuations or cavities in the plasmasphere.

  19. The Chelyabinsk Meteorite as a multiple source of acoustic and seismic waves

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Shock waves and impact of the Chelyabinsk Meteorite fragments on the ground initiated various waves in the atmosphere and the earth. Three different sources of seismic and infrasound waves were found by arrival time and azimuth of seismic and infrasound waves recorded by the International Monitoring System.

  20. XMM follow-up observations of two unidentified INTEGRAL sources

    NASA Astrophysics Data System (ADS)

    Molina, M.; Landi, R.; Bassani, L.; Bazzano, A.; Fiocchi, M.; Bird, A. J.; Drave, S. P.

    2012-07-01

    We report the results of X-ray follow-up observations performed with XMM-Newton of two unidentified hard X-ray sources, AX J1753.5-2745 and IGR J17348-2045 listed in the INTEGRAL/IBIS 9-year Galactic Hard X-ray Survey (Krivonos et al. 2012, arXiv:1205.3941) and in 4th IBIS Survey Catalogue (Bird et al. 2010, ApJS, 186, 1) respectively. We assume a conservative XMM positional uncertainty of 5".

  1. Monitoring of Ash Ejection from Ecuadorean Volcanoes Using Infrasound

    NASA Astrophysics Data System (ADS)

    Hetzer, C.; Garces, M.; Fee, D.; Bass, H.; McCormack, D.

    2007-12-01

    Two infrasound arrays with 100-meter apertures have been deployed in Ecuador in order to monitor volcanic eruptions that may produce ash clouds. Data is collected continuously and streamed via satellite and internet links to processing centers that apply array processing techniques to display acoustic detections of volcanic eruptions in near-real-time. These data products are delivered to the DC Volcanic Ash Advisory Center (VAAC), and have been used as additional confirmation of an eruption in ash advisories provided by the VAAC to commercial aircraft. Considerable research has been put into identifying the types of acoustic signals that indicate ash injection, as well as eliminating false alarms and reducing the latency between data collection and notification. Research conducted to date will be discussed, as well as several case studies wherein infrasound data proved useful for quick detection of eruptions. A brief summary of the advantages gained from use of this technique will also be presented.

  2. 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.

  3. 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

  4. The developement of the Romanian infrasound network array

    NASA Astrophysics Data System (ADS)

    Ionescu, C.; Moldovan, A. S.; Moldovan, I. A.; Grigore, A. G.

    2009-04-01

    The infrasound technology in Romania was developed in the framework of three national projects in the field of Monitoring of anomalous phenomena associated with earthquakes, explosions and storms with the very start in 2005. In the last years we have developed in the epicentral zone two triangle-shaped infrasound arrays, the first one having 400 m aperture and the second one 2.5 km aperture. The sites are also equipped with seismic, electric and triaxial fluxgate magnetic sensors. First configuration, surrounding a central point (Plostina-Vrancea) have been completed with other three sites with a larger aperture, needed for a better event azimuth identification. In one site there are installed two types os sensors for reliability studies. At present the infrasound array from Plostina consists in 6 elements: three elements built in Basic Design Requirements for Pipe Arrays with Chaparral sensors (Model25, 0.1Hz to 200 Hz) and Quantera 330 digitizer with porous pipe garden house installed on external ring and the other three with MBAZEL2007 (+/-50Pa) microbarometer with porous pipe and Hi6 digitizer.

  5. 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.

  6. 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.

  7. Anthropogenic carbon dioxide source regions observed from space

    NASA Astrophysics Data System (ADS)

    Schneising, Oliver; Heymann, Jens; Buchwitz, Michael; Reuter, Maximilian; Bovensmann, Heinrich; Burrows, John P.

    2013-04-01

    Urban areas, which are home to the majority of today's world population, are responsible for more than two-thirds of the global energy-related carbon dioxide emissions. Given the ongoing demographic growth and rising energy consumption in metropolitan regions particularly in the developing world, urban-based emissions are expected to further increase in the future. As a consequence, monitoring and independent verification of reported anthropogenic emissions is becoming more and more important. It is demonstrated using CO2 column-averaged mole fraction data retrieved from the SCIAMACHY instrument onboard ENVISAT that anthropogenic CO2 emissions can be detected from space and that emission trends might be tracked using satellite observations. This is promising with regard to future satellite missions with high spatial resolution and wide swath imaging capability aiming at constraining anthropogenic emissions down to the point-source scale. By subtracting retrieved background values from those retrieved over urban areas the regional contrasts are quantified and significant CO2 enhancements are found for several anthropogenic source regions around the world. The order of magnitude of the enhancements is in agreement with what is expected for anthropogenic CO2 signals. The validity of the retrieved spatial enhancement patterns and of the temporal trends of the retrieved enhancements is assessed by comparison with anthropogenic emissions from the Emission Database for Global Atmospheric Research (EDGAR).

  8. Effects of infrasound on the growth of bone marrow mesenchymal stem cells: a pilot study.

    PubMed

    He, Renhong; Fan, Jianzhong

    2014-11-01

    Poor viability of transplanted bone marrow mesenchymal stem cells (BMSCs) is well‑known, but developing methods for enhancing the viability of BMSCs requires further investigation. The aim of the present study was to elucidate the effects of infrasound on the proliferation and apoptosis of BMSCs, and to determine the association between survivin expression levels and infrasound on BMSCs. Primary BMSCs were derived from Sprague Dawley rats. The BMSCs, used at passage three, were divided into groups that received infrasound for 10, 30, 60, 90 or 120 min, and control groups, which were exposed to the air for the same durations. Infrasound was found to promote proliferation and inhibit apoptosis in BMSCs. The results indicated that 60 min was the most suitable duration for applied infrasound treatment to BMSCs. The protein and mRNA expression levels of survivin in BMSCs from the two treatment groups that received 60 min infrasound or air, were examined by immunofluorescence and quantitative polymerase chain reaction. Significant differences in survivin expression levels were identified between the two groups, as infrasound enhanced the expression levels of survivin. In conclusion, infrasound promoted proliferation and inhibited apoptosis in BMSCs, and one mechanisms responsible for the protective effects may be the increased expression levels of survivin. PMID:25175368

  9. 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.

  10. 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