Download
seimoacoustics from kilauea volcano using multiple arrays n.
Skip this Video
Loading SlideShow in 5 Seconds..
Seimoacoustics from Kilauea Volcano using multiple arrays PowerPoint Presentation
Download Presentation
Seimoacoustics from Kilauea Volcano using multiple arrays

Seimoacoustics from Kilauea Volcano using multiple arrays

103 Views Download Presentation
Download Presentation

Seimoacoustics from Kilauea Volcano using multiple arrays

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Seimoacoustics from Kilauea Volcano using multiple arrays David Fee and Milton Garces Infrasound Laboratory Univ. of Hawaii, Manoa dfee@isla.hawaii.edu Tim Orr, David Wilson US Geological Survey Hawaiian Volcano Observatory

  2. Overview • Introduction to Kilauea • Arrays • Observations in Chronological Order • Multiple types of tremor • Skylight Detection • Two fissure eruptions • Acoustic energy vs. seismic/tilt event • Conclusions

  3. Pu`u` O`o Crater Complex • Pu`u O`o crater complex is the active section of Kilauea Volcano • Nearly continuous effusion and degassing from multiple vent system since 1992 • Lava flowed from the crater complex ~13 km through a complicated conduit system until it met the ocean • Multiple open vents and lava tube skylights appear active • System changed in June 2007  fissure eruptions

  4. Infrasound Arrays – MENE MENE Array • Semi-permanent • 12.5 km from Pu`u O`o • Dense Jungle • Since 9/06

  5. Infrasound Arrays – KIPU KIPU Array • 2 week deployment in 4/07 • 2.5 km from Pu`u O`o • High S/N • Collocated BB Seis

  6. STC Seismometer Infrasound Arrays - ZION ZION Array • Since 9/07 • 7 km from Pu`u O`o • 6.5 km from Fissure D • Better azimuthal resolution • Results preliminary

  7. Infrasonic Tremor for 12/1/2006 • Usually constant between ~0.5-3 Hz • Harmonic, gliding tremor as well • Broad harmonics (~2 Hz) • High Attenuation? • Gliding (spectral peaks change frequency over time) • Magma level may define effective length of conduit • Seismic spectrogram from same period has relatively uniform tremor, some harmonics • Tremor not visible in waveforms

  8. KIPU KIPU results – Tremor and Skylight • PMCC Detections: 4/22/07 1510-1525 • Nearly all signal originated from Pu`u O`o • Discovered skylight along lava tube system • Intermittently acoustic active, both audible and infrasound • Possible to discriminate between the two sources • Need confirmation of detection…

  9. KIPU results – 4/22/07 0600-0800 UTC • A sharp, complex spectral peak of ~0.6 Hz is present at KIPU and MENE • Tends to bifurcate and shift frequency over time • Seismic wavefield is complex and path effects appear to be present, but spectral peak is also manifested • Broadband infrasound signal as well Black-2.5 km inf Red-13 km inf Blue-seismic

  10. Episode 56 • EQ swarm begins around 6/17 1415 UTC on upper east rift zone near Mauna Ulu • Magma intrusion 1.5-3 km deep • Puu Oo Vent collapses on 6/18 • First impulsive acoustic events at Puu Oo • Relatively long duration

  11. Fissure Opening? Episode 56 – Fissure Opening • Infrasound signals around 1015-1045 UTC from ~132° • Fissure Opening?

  12. Episode 56 - Resuts • 200 m long fissure opens 6 km west of on 6/19 • Steam, gas, and lava • Infrasound recordings from 0900-1100 UTC pm 6/19 • Focused between 2-10 Hz, doesn’t look like surf or cultural • Not constrained well by any other technology • Harmonics present • Similar to Puu Oo

  13. Fissure Eruption – 7/21/2007 • Magma drained from Pu`u O`o around 1000 UTC • Eruption moved eastward along a set of fissures – strong infrasound! • Seismically quiet, video blocked by poor weather

  14. Fissure Eruption- 8/22/07 • Increased tremor signals in late August • Activation of harmonics around 2000 UTC • Increased activity prompted installation of second array in Glenwood

  15. Fissure Eruption – 7/21/2007: Single array • Fissure signal concentrated between 1.5-5 Hz, similar to Puu Oo • No harmonics

  16. PO FD ZION Results – 2007/9/17 • Tremor signals switch on to Puu Oo on 9/17? • Puu Oo still actively degassing • Standing Hypothesis • Magma interacting with the gas • Many ways of producing this process • Want to model broad spectral peak

  17. Fissure Eruptions Daily Acoustic Energy Calculation • Calculate acoustic source energy for tremor • To differentiate between signal and noise, the acoustic energy is only calculated during times of coherent signal from the specified azimuth. • Split data into 60 sec windows • Mean correlation value for window must be above threshold • Minimum number of pixels per window EAcoustic=2πr2/ρc ∫ΔP(t)2dt r=source-receiver distance ρ=air density C=sound speed ΔP=change in pressure

  18. Acoustic Energy vs. RSAM/Tilt • Event 1: 8/24 00:02 UTC (8/23 14:02 HST) • Collapse Event: • Significant drop-off in acoustic energy (tremor) in the days following this collapse event. • Event preceded by 3 days of high acoustic tremor and RSAM values. • No impulsive acoustic signal recorded at the time of the seismic/tilt event. Minor earthquake recorded by the infrasound sensors around 0000 UTC. • Collapse event may have changed magma/degassing dynamics.

  19. Acoustic Energy vs. RSAM/Tilt • Event 2: 8/29 1100-1400 UTC (8/29 0100-0400 HST) • Tremor Event • Strong acoustic and seismic tremor during this 3 hour time period, originating from P‘u‘u ‘O‘o, not Fissure D. • Infrasound signal concentrated between 1220-1400 UTC, is below 3 Hz, Collapse event may have changed magma/degassing dynamics. • Infrasound signal decreased rapidly at 1400 UTC and returns to similar azimuth as Fissure D. • No longer-term variation in acoustic energy or RSAM apparent. • Similar “burst” of tremor occurred on 9/17 around 0900 UTC.

  20. Acoustic Energy vs. RSAM/Tilt • Event 3: 9/3 0152 UTC (9/2 1552 HST) • Collapse Event: • Nothing out of the ordinary recorded acoustically at the time of this collapse event. • However, tremor energy levels decreased to near zero in the days following. Collapse event may have changed dynamics as well.

  21. Conclusions – Future Work • Identification of new sources (skylight, fissures) made at Kilauea • Tremor observations consistent with pressure oscillations resulting from unsteady magma flow within tubes/conduits • P‘u‘u ‘O‘o tremor between 0.5 – 3 Hz fairly constant in both infrasound and seismic recordings before 6/18 • Higher frequency harmonic, gliding tremor more intermittent and possibly due to excitation of conduit • Sharp spectral peaks in infrasound and seismic – same resonating source? • Comparison of seismic, infrasound, and tilt data help explain dynamics and overall volcanic activity levels