What’s the big fuss about Harmonic Tremor on Volcanoes? - PowerPoint PPT Presentation

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What’s the big fuss about Harmonic Tremor on Volcanoes?

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  1. What’s the big fuss about Harmonic Tremor on Volcanoes? Jonathan M. Lees New Mexico Tech, 2009

  2. Where is it observed? Karymsky, Kamchatka Arenal, Costa Rica Sangay, Ecuador Reventador, Ecuador Tungurahua, Ecuador *Santiaguito, Guatemala (Semeru, Merapi…others?)

  3. http://www.seismo.com/msop/nmsop/13 volcano/volcano2/volcano2.html Typical VT event at Mt. Merapi, Indonesia a) typical example of a VT-B type event recorded during a high activity phase at Mt. Merapi. Note that the overall frequency content is mainly between 1 — 10 Hz with a dominant frequency at roughly 3 Hz. b) zoomed out version of the same event in its three components. Whereas the P-wave arrival is clearly visible, no clear S-wave arrival can be seen. The circle marks the wavelet that has the approximate S-wave travel time for the estimated source location

  4. a) example of a LF-wave group recorded at Mt. Merapi. Clearly the dominant frequency is around 1 Hz. b) shows an example of a LF event recorded at two different sites located at Redoubt volcano, Alaska (courtesy of S. McNutt, Alaska Volcano Observatory; AVO). The spindle shaped signal is also known as Tornillo. Low Frequency Events

  5. Harmonic tremor signal recorded at Mt. Semeru, Indonesia. Up to six overtones can be recognized starting with a fundamental mode located at roughly 0.8 Hz.

  6. Typical Karymsky Chugging Event, 1997 Initial explosion Chugging Acoustic Vertical North-South East-West

  7. Simple Harmonic Motion Sinusoid : 5 Hz (sample rate = 0.001)

  8. Sinusoids with 4 frequencies, 5,10, 15, 20

  9. Ten harmonics, 5 through 50 Hz

  10. 10 Random Frequencies

  11. 10 frequencies around the harmonics randomly perturbed

  12. 10 frequencies around harmonics with slight perturbation

  13. Harmonic Tremor • Common on Volcanoes • Provides Constraints for Conduits: • Geometry • Composition • Density • Visco-elastic parameters

  14. Many researchers have contributed to the study of Harmonic Tremor • K. Aki & M. Fehler • B. Crosson • B. Chouet • B. Julian • S. McNutt • M. Ripepe • V. Schlindwein • M. Hellweg • E. Gordeev • T. Ohminato • M. Garces • M. Yamamoto • H. Kumagai • T. Nishimura • R. Leet • K. Konstantinou (review) In this presentation we are concerned with tremor that is accompanied by infrasonic emission

  15. Note Tremor on Seismic ?

  16. Reventador tremor

  17. Reventador tremor

  18. Reventador tremor

  19. Reventador tremor

  20. Seismo-Acoustic Tremor:Chugging • Observed when seismic and acoustic waves are discerned and correlated • Examples: • Arenal(Benoit & McNutt, 1997; Garces, 1998; Hagerty et al. 2000) • Karmysky(Johnson & Lees, 1999; Lees et al. 2004) • Sangay (Johnson & Lees, 1999; Lees & Ruiz, 2008) • Reventador(Lees et al., 2008) • Tungurahua (Ruiz et al., 2005) • Fuego (Lyons et al.) • Santiaguito (Lees et al.)

  21. Chugging Illustrated Slow Fast Video

  22. Infrasound Chugging at Karymsky, 1997 While there are similarities between these chugging sequences, there is also considerable variability.

  23. Examples of Chugging at Sangay Volcano

  24. Chugging Spectrum Chugging Sound: Gliding

  25. Karymsky Infrasound, 1997 Fundamental Mode….and Harmonics?

  26. Karymsky Infrasound, 1997

  27. Numerous episodes of seismo-acoustic tremor exhibit fundamental frequencies ranging between 0.7 to 1.4 Hz. 21 chugging events at Karymsky

  28. Karymsky, tremor (chugging)

  29. V = vertical I = Infrasound Santiaguito Explosion from 2009

  30. Zoom of Santiaguito explosion, 2009

  31. What is the best model to explain these physical phenomena? Active vent

  32. V. Schlindwein M. Garces S. Mcnutt Others… J. Johnson J. Lees M. Hellweg M. Hellweg

  33. Possible Physical Models • Harmonic Oscillations – Organ Pipe Modes? • Periodic Bubble/Slug Formation? • Flow Past Small Obstruction? • Cork/Viscous Plugging – Pressure Cooker Modes

  34. Milton Garces’ Model: Organ Pipe Modes Arenal Volcano, Costa Rica

  35. Garces Approach: Model Fourier Spectrum

  36. Organ Pipe Mode Explanation of Volcano Chugging Rijke Tube Excitation of fundamental modes And harmonics in a column of fluid

  37. Resonating Cylindrical Conduits Integer Harmonics Odd Integer Harmonics Integer Harmonics Open-Open Open-Closed Closed-Closed

  38. Correlation of interval time and amplitude: indication of non-linear, feed back mechanism Linear Trends Sangay Karymsky

  39. Slope Analysis: Amplitude vs Time Delay Positive slopes Sangay, Ecuador Multiple Chugging Events

  40. Chugging at Santiaguito: Linear amplitude-repose time until change in vent modifies relationship in time.

  41. Pressure Cooker Model Steam Vent

  42. Set of coupled, non-linear Differential Equations Lees and Bolton (1999) Damping Acceleration of plug Non-negative Ram effect Pressure in Pot Number of Molecules in Pot Pressure in Vent

  43. Back of the envelope calculation plug Cone plug, radius R=20m, height h=20m Force = .2×109N Pressure = .1 MPa Pressure Cooker, Lees and Bolton, 1999