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Real-time infrasound localization on active Italian volcanoes

This study focuses on real-time localization of infrasound signals from Italian volcanoes, specifically Stromboli and Etna. The study analyzes the seismic and infrasonic signals to infer source dynamics within the shallow plumbing system of the volcanoes.

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Real-time infrasound localization on active Italian volcanoes

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  1. Real-time infrasound localization on active Italian volcanoes E. Marchetti, M. Ripepe, G.Ulivieri and G. Lacanna Dipartimento di Scienze della Terra, Università di Firenze, Italy

  2. multi vents systems Infrasonic arrays monitoring Italian Volcanoes Stromboli: 2003 - present Etna: 2006 - present

  3. explosions Sample of infrasound: Stromboli gas bursting

  4. gas bursting - ~1-20 Pa at 500 m from the source - recurrence time of ~ 2 sec Sample of infrasound: Stromboli explosions - ~10-100 Pa at 500 m from the source -10-20 events/hour

  5. Real-Time Source Location: - background Near source array deployment (spherical wave propagation NO PLANE WAVE) Large signal-to-noise ratio - requirements Fast computing time High spatial resolution Real-time visualisation of the source position and evaluation of excess pressure at the source - procedure Grid searching with assumption: plane at fixed elevation spherical propagation in an homogeneous medium

  6. 1. Grid definition 2. time shift between records, assuming constant velocity 3. semblance between pairs of record 4. semblance across the array Filtering out non-volcanic phenomena Real-Time Source Location: grid searching:

  7. Real-Time Source Location: Real-Time Array Processing

  8. Real-Time Source Location: grid searching, Etna 19 Oct 2006_23:26:45 Map of Semblance Distribution and BackAzimuth Direction

  9. FDTD model Topography into account assuming: perfectly reflecting surface modeled with stair stepping • - no wind • homogeneous atmosphere • no attenuation • cell 5x5 m • pressure at 10 m from the surface • source in air at 25 m from the surface

  10. Located source Theoretical pressure waves Good azimuthal resolution The fixed-plane and homogeneous medium assumptions do not affect the result FDTD model Source position

  11. 1° Real-Time Source Location: grid searching, Etna 19 Oct 2006_22:48:45 Map of Semblance Distribution Map of Semblance Distribution and BackAzimuth Direction

  12. Real-Time Source Location: grid searching, Etna 19 Oct 2006_22:49:30 24° Map of Semblance Distribution and BackAzimuth Direction

  13. Real-Time Source Location: grid searching, Etna 19 Oct 2006_22:53:10 Map of Semblance Distribution and BackAzimuth Direction

  14. Real-Time Source Location: grid searching, Etna 19 Oct 2006_23:01:55 Map of Semblance Distribution and BackAzimuth Direction

  15. Real-Time Source Location: grid searching, Etna 19 Oct 2006_23:03:50 Map of Semblance Distribution and BackAzimuth Direction

  16. Real-Time Source Location: grid searching, Etna 20 Oct 2006_23:48:10 Map of Semblance Distribution and BackAzimuth Direction

  17. Real-Time Source Location: grid searching, Etna 22 Sept 2006_23:03:50 Map of Semblance Distribution and BackAzimuth Direction

  18. Real-Time Source Location: grid searching, Etna 19 Oct 2006_23:26:45 Map of Semblance Distribution and BackAzimuth Direction

  19. Real-Time Source Location: grid searching, Etna 20 Oct 2006_23:01:20 Map of Semblance Distribution and BackAzimuth Direction

  20. Real-Time Source Location: grid searching, Etna 22 Sept 2006_11:18:25 Map of Semblance Distribution and BackAzimuth Direction

  21. Real-Time Source Location: grid searching, Etna 22 Sept 2006_11:15:25 Map of Semblance Distribution and BackAzimuth Direction

  22. 7 1 -10 24 Real-Time Source Location: grid searching, Etna 217000 infrasonic transients located in 58 days • Infrasonic Amplitude and - propagation back-azimuth of infrasonic sources

  23. back-azimuth of infrasound released Sept. 09 - Nov. 6, 2006 SE NE VG BN # transients located ~ 217,000

  24. Real-Time Source Location: grid searching, Stromboli

  25. 300° 290° 280° 270° 260° 250° Real-Time Source Location: azimuth scanning, Stromboli Semblance Distribution Jan, 31, 2004 12:00-21:00

  26. gas bursting explosions    > Bubbly flow at bifurcations? - Drops are travelling along branches with high Flux - Whenever Flux Changes, Drops change their path Flux Manga, J. Fluid Mech., 1996 infrasonic back-azimuth - Gas bursting stable form hours to days - Degassing changes abruptly from vent to vent

  27. 2003 2004 NE C # detections ~ 4 millions # detections ~ 5 millions 2005 2006 NE C C # detections ~ 6.5 millions # detections ~ 3 millions Changes in volcanic activity: 2003-2006

  28. log-log excess-pressure distribution of infrasonic transients: 2003 - 2006 degassing explosions gas bursting and explosions are not produced by a scale-invariant process: Evidence for a Different Dynamics?

  29. Polarization of VLP seismic transients Source Location of different active vents Stromboli May 7-8, 2006

  30. Source Location of different active vents Diapositiva 30 Stromboli May 7-8, 2006

  31. comparison of typical infrasonic transients

  32. comparison of stacked ground displacement Different vents are associated with significantly different seismic and infrasonic signals

  33. conclusions • efficiency of infrasound arrays describing activity at multi vents volcanoes, and inferring source dynamics withing the shallow plumbing system • SIMPLE & FAST Real-time source location based on semblance across the array • grid-searching / azimuth-scanning at fixed propagation velocity Fast computing time and filter for non-volcanic processes • Array analysis --> how and when single vents are active (monitoring - research)

  34. FDTD: infrasound propagation

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