Assessing and optimizing infra-sound networks to monitor volcanic eruptions
Description
Understanding infra-sound signals is essential to monitor compliance with the Comprehensive Nuclear-Test ban Treaty, and also to demonstrate the potential of the global monitoring infra-sound network for civil and scientific applications. The main objective of this thesis is to develop a robust tool to estimate and optimize the performance of any infra-sound network to monitor explosive sources such as volcanic eruptions. Unlike previous studies, the developed method has the advantage to consider realistic atmospheric specifications along the propagation path, source frequency and noise levels at the stations. It allows to predict the attenuation and the minimum detectable source amplitude. By simulating the performances of any infra-sound networks, it is then possible to define the optimal configuration of the network to monitor a specific region, during a given period. When carefully adding a station to the existing network, performance can be improved by a factor of 2. However, it is not always possible to complete the network. A good knowledge of detection capabilities at large distances is thus essential. To provide a more realistic picture of the performance, we integrate the atmospheric longitudinal variability along the infra-sound propagation path in our simulations. This thesis also contributes in providing a confidence index taking into account the uncertainties related to propagation and atmospheric models. At high frequencies, the error can reach 40 dB. Volcanic eruptions are natural, powerful and valuable calibrating sources of infra-sound, worldwide detected. In this study, the well instrumented volcanoes Yasur, in Vanuatu, and Etna, in Italy, offer a unique opportunity to validate our attenuation model. In particular, accurate comparisons between near-field recordings and far-field detections of these volcanoes have helped to highlight the potential of our simulation tool to remotely monitor volcanoes. Such work could significantly help to prevent eruption disaster and mitigate the impact of ash clouds on aviation. (author)
Abstract (French)
La comprehension des signaux infrasons est fondamentale pour satisfaire aux exigences du Traite d'Interdiction Complete des Essais nucleaires, mais aussi pour demontrer le potentiel du reseau global de surveillance pour des application civiles et scientifiques. L'objectif principal de cette these est de developper un outil robuste d'estimation et d'optimisation des capacites de detection d'un reseau arbitraire de stations infrasons, pour la surveillance de sources explosives, dont notamment une application aux eruptions volcaniques. Contrairement aux etudes anterieures, la methode developpee a l'avantage de considerer des specifications atmospheriques realistes le long du trajet, des caracteristiques frequentielles des signaux d'interet et des niveaux de bruit aux stations. Elle permet de predire l'attenuation de l'amplitude acoustique le long du trajet, ainsi que l'amplitude minimale detectable par le reseau. En simulant les performances de n'importe quels reseaux infrasons, il est ensuite possible de definir l'agencement optimal des stations qui assurera la meilleure surveillance possible d'une region specifique, pendant une periode donnee. En choisissant avec precaution l'emplacement d'une station a ajouter au reseau existant, les performances peuvent etre amelioree par un facteur 2. D'autre part, il n'est pas toujours possible de completer le reseau. Une bonne connaissance des capacites de detections a des grandes distances est alors essentielle. En integrant la variabilite longitudinale des conditions atmospheriques le long du trajet de propagation des infrasons, nos simulations d'attenuation permettent de fournir une image plus realiste des performances. Un des apports de cette these concerne aussi la production d'un indice de confiance prenant en compte les incertitudes liees au modele de propagation utilise ainsi qu'aux modeles atmospheriques. Aux hautes frequences, l'erreur sur l'attenuation peut atteindre 40 dB dans des conditions de vents faibles. Les eruptions volcaniques sont des sources naturelles de calibration d'infrasons. Dans cette etude, les volcans bien instrumentes du Yasur, au Vanuatu, et de l'Etna, en Italie, offrent une occasion unique pour valider notre modele d'attenuation. En particulier, les comparaisons precises entre les enregistrements en champ proche et lointain de ces volcans ont permis de mettre en avant le potentiel de notre outil de simulation pour la surveillance. De tels travaux pourraient contribuer significativement a la prevention de catastrophes et a l'attenuation de l'impact du nuage de cendres sur le trafic aerien
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Additional details
Additional titles
- Original title (French)
- Evaluation et optimisation de reseau infrason pour la surveillance volcanique
Identifiers
Publishing Information
- Imprint Pagination
- 279 p.
- Report number
- FRCEA-TH--9027
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 49015628
- Subject category
- S07: ISOTOPES AND RADIATION SOURCES; S98: NUCLEAR DISARMAMENT, SAFEGUARDS AND PHYSICAL PROTECTION;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- ATTENUATION; COMPUTERIZED SIMULATION; DATA COVARIANCES; MONITORING; NUCLEAR EXPLOSION DETECTION; PERFORMANCE
- Descriptors DEC
- DETECTION; SIMULATION
Optional Information
- Notes
- 270 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS website for current contact and E-mail addresses: http://www.iaea.org/inis/Contacts/; Also available from Bibliotheque, Institut de Physique du Globe de Paris, 1 Rue Jussieu, 75005 Paris (France)