ANOMALOUS SEISMO-ACOUSTIC WAVE PROPAGATION AND DETERMINATION SOURCE OF INFRASOUND

The network of infrasound stations (I34MN) in Mongolia daily registers set of infrasound from various sources besides explosions. The data from explosions in mines in region and from other sources detected since 2000 to 2009 in seismic and infrasound stations is analyzed. The analysis these signals dependence of speed distribution of sound from seasonal, wind forces and direction moreover on short distances. From detected in infrasound stations (I34MN) in year 80-90 % of signals make microbaroms, the wide range of their sources is visible from the frequency analysis. From the general analysis registered seismo and acoustic signals of explosions on the seismic and infrasound networks stations miscalculate not only speeds of distribution of sounds on close distances (50-500 km),  and also the speed model of atmosphere is made

Analysis of Infrasound Propagation at Regional Distance by Mining Explosion

Seismic and acoustic recordings are particularly important to help identifying and locating industrial blasting sources. We have analyzed seismo-acoustic signals from mine blast for 2000 and 2005 in order to determine detection seismo-acoustic signals of explosion by seismic and infrasound stations. Several large mines in the region routinely generate explosions that are detected seismically and with infrasound. The mine range in distance from 40-500 km from the seismic, infrasound array. In last few years mining activity in Mongolia significantly increased. All events identified as quarry blasts have occurred during daytimes between 03:00 p.m. and 08:00 a.m. GMT and on weekdays from Monday to Friday. The corresponding number of infrasound detection is found to be dependent upon the regional weather condition, which is included air temperature, epicentral distance, wind force and velocity. We present the seismic and infrasound IMS stations and some results of analysis.DOI: http://dx.doi.org/10.5564/pmas.v0i4.45 Proceedings of the Mongolian Academy of Sciences 2009 No 4 pp.42-5

Local, Regional, and Remote Seismo‐Acoustic Observations of the April 2015 VEI 4 Eruption of Calbuco Volcano, Chile

The two major explosive phases of the 22–23 April 2015 eruption of Calbuco volcano, Chile, produced powerful seismicity and infrasound. The eruption was recorded on seismo-acoustic stations out to 1,540 km and on five stations (IS02, IS08, IS09, IS27, and IS49) of the International Monitoring System (IMS) infrasound network at distances from 1,525 to 5,122 km. The remote IMS infrasound stations provide an accurate explosion chronology consistent with the regional and local seismo-acoustic data and with previous studies of lightning and plume observations. We use the IMS network to detect and locate the eruption signals using a brute-force, grid-search, cross-bearings approach. After incorporating azimuth deviation corrections from stratospheric crosswinds using 3-D ray tracing, the estimated source location is 172 km from true. This case study highlights the significant capability of the IMS infrasound network to provide automated detection, characterization, and timing estimates of global explosive volcanic activity. Augmenting the IMS with regional seismo-acoustic networks will dramatically enhance volcanic signal detection, reduce latency, and improve discrimination capability

How Can the International Monitoring System Infrasound Network Contribute to Gravity Wave Measurements?

Gravity waves (GWs) propagate horizontally and vertically in the atmosphere. They transport energy and momentum, and therefore GWs can affect the atmospheric circulation at different altitude layers when dissipating. Thus knowledge about the occurrence of GWs is essential for Numerical Weather Prediction (NWP). However, uniform networks for covering GW measurements globally are rare, especially in the troposphere. It has been shown that an infrasound station of the International Monitoring System (IMS) infrasound network is capable of measuring GWs at the Earth’s surface. The IMS was deployed for monitoring the atmosphere to verify compliance with the Comprehensive Nuclear-Test-Ban-Treaty. In this study, the Progressive Multi-Channel Correlation Method (PMCC) is used for re-processing up to 20 years of IMS infrasound recordings in order to derive GW detections. For this purpose, two alternative PMCC configurations are discussed, covering GW frequencies equivalent to periods of between 5 min and 150 min. These detections mainly reflect sources of deep convection, particularly in the tropics. At mid-latitudes, coherent wind noise more often produces spurious detections. Combining the results of both configurations provides a global dataset of ground-based GW measurements, which enables the calculation of GW parameters. These can be used for improving NWP models

Infrasound Monitoring for Atmospheric Studies

International audienceThe infrasound field, the science of low-frequency acoustic waves, has developed into a broad interdisciplinary field encompassing academic disciplines of physics and recent technical and scientific developments. The infrasound network of the International Monitoring Network (IMS) of the CTBT-Organization has demonstrated its capability for detecting and locating infrasonic sources such as meteorites, volcanic eruptions, earthquakes, auroras, mountain associated waves... Nearly 70% of the global network is now operational and regional cluster arrays are deployed around the globe. Systematic investigations into low-frequency acoustic signals have evidenced an unprecedented potential of the monitoring of infrasonic waves permanently generated by natural and man-made events. Furthermore, recent studies point out new insights on quantitative relationships between observables and atmospheric specifications, and therefore opening new fields into the mathematics of geophysical inverse problems for atmospheric remote sensing. This volume reviews the most important areas of infrasound, with emphasis on the latest researches and applications, e.g. instrumentation, engineering, signal processing, source monitoring, propagation modeling, atmospheric dynamics, global changes, remote sensing methods. Researchers and students will benefit from a comprehensive content of infrasound related topics, where both fundamental and applied topics are discussed by authors from international institutions, all experts in their fields

Assessing uncertainties in infrasound network performance modelling: application to the Euro-Mediterranean and Southeast Asian region

We propose a modelling technique to confidently estimate and optimize the performance of any infrasound network to remotely monitor sources of interest such as volcanic eruptions, while considering realistic atmospheric specifications along the propagation path, source frequency and noise levels at the station. To provide a more realistic picture of the network performance, we define a confidence level accounting for propagation and atmospheric uncertainties. Therefore, we consider 'numerical' uncertainties linked to the approximations made in the used propagation model, errors of the developed mathematical model and atmospheric uncertainties derived from measurement campaigns. In parallel, we perform a sensitivity analysis to determine how each input parameter contributes to the developed mathematical model output as well as to the attenuation model output. Such study is helpful for model simplification and uncertainty reduction by identifying, and thus paying more attention to the most influential model inputs. Below 1 Hz, the effect of 'numerical' errors on network performance modelling dominates. The same situation is observed during strong and stable downwind stratospheric winds along propagation paths. Conversely, when propagation occurs upwind, atmospheric uncertainties become predominant as the frequency increases. This method is then applied to assess the performance of the International Monitoring System (IMS) infrasound network in the Euro-Mediterranean and the Southeast Asian regions. We highlight a frequency, seasonal and spatial dependence of uncertainties in the modelling. Below 1 Hz, large errors are predicted in the shadow zone but the overall error is less than 20 dB. Above 1 Hz, errors with same order of magnitude are also observed, when strong stratospheric jets prevail. But during weak stratospheric duct, uncertainties associated to the modelled attenuation may exceed 30 dB. Such studies lead to significant improvement in assessing detection capability of infrasound network, which is of great interest for monitoring artificial or natural explosive sources like volcanic eruption. In particular this work will contribute into designing and prioritizing maintenance of any given infrasound network, in order to provide even better and more accurate predictions.Ministry of Education (MOE)National Research Foundation (NRF)Published versionThis research was supported by the Earth Observatory of Singapore via its funding from the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative. This work comprises EOS contribution number 405

Infrasound Monitoring for Atmospheric Studies. Challenges in Middle-atmosphere Dynamics and Societal Benefits

International audienceSince the publication of the first volume “Infrasound monitoring for atmospheric studies” published in 2010, significant advances were achieved in the fields of engineering, propagation modelling, and atmospheric remote sensing methods. The global infrasound network, which consists of the International Monitoring Network (IMS) for nuclear test ban verification completed by an increasing number of regional cluster arrays deployed around the globe, has evidenced an unprecedented potential for detecting, locating and characterizing various natural and man-made sources. In recent years, infrasound has evolved into a broad interdisciplinary field encompassing academic disciplines of geophysics and innovative technical and scientific developments. The advances in innovative ground-based instruments, including infrasound inversions for continuous observations of the stratosphere and mesosphere, provide useful insights into the geophysical source phenomenology and atmospheric processes involved. Systematic investigations into low-frequency infrasound signals and the development of complementary observational platforms point out new insights into the dynamics of the middle atmosphere which play a significant role in both tropospheric weather and climate. This monitoring system also provides continuous relevant information about natural hazards with high societal benefits, like on-going volcanic eruptions, surface earthquakes, meteorites or severe weather. With this new edition, researchers and students benefit from a comprehensive content of both fundamental and applied inter-disciplinary topics

Mountain-Associated Waves and their relation to Orographic Gravity Waves

Infrasound covers frequencies of around 10−3 Hz to approximately 20 Hz and can propagate in atmospheric waveguides over long distances as a result of low absorption, depending on the state of the atmosphere. Therefore, infrasound is utilized to detect atmospheric explosions. Following the opening of the Comprehensive Nuclear-Test-Ban Treaty for signature in 1996, the International Monitoring System (IMS) was designed to detect explosions with a minimum yield of one kiloton of TNT equivalent worldwide. Currently 51 out of 60 IMS infrasound stations are recording pressure fluctuations of the order of 10−3 Pa to 10 Pa. In this study, this unique network is used to characterize infrasound signals of so-called Mountain-Associated Waves (MAWs) on a global scale. MAW frequencies range from 0.01 Hz to 0.1 Hz. Previous observations were constrained to regional networks in America and date back to the 1960s and 1970s

Evaluating the performance of infrasound detectors

International audience<p>Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has deployed more than 60 stations around the world todetect the presence of infrasound in the atmosphere and then measure their characteristics more particularly the direction ofarrival (DOA) and the velocity. Many recent studies have been devoted to infrasound signal processing, more particularly to thedetection problem. Let us cite R. H. Shumway in 2001, S. J. Arrowsmith in 2008, David J. Brown in 2008, W. B. Howard in2010, K. Walker in 2010.In 1995, Y. Cansi has been a pioneer in infrasonic signal processing with the PMCC method. In PMCC, the detection processis based on the sum of Time Difference of Arrivals around any triangle of sensors. More recently we have been presented GLRTapproach and given comparative results with PMCC and Fisher statistic.Here we propose to extend this comparison through the creation of a benchmark database. Based on simulation with asemi-realistic propagation model and observed signals from IDC (IRED), performance of the detection methods are compared bycomputing the Receiver Operating Characteristic (ROC) curves.</p