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Seimoacoustics from Kilauea Volcano using multiple arrays

David Fee and Milton GarcesDavid Fee and Milton Garces

Infrasound LaboratoryInfrasound Laboratory

Univ. of Hawaii, ManoaUniv. of Hawaii, Manoa

dfee@isla.hawaii.edudfee@isla.hawaii.edu

Tim Orr, David WilsonTim Orr, David Wilson

US Geological SurveyUS Geological Survey

Hawaiian Volcano Observatory Hawaiian Volcano Observatory

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Overview

• Introduction to Kilauea Introduction to Kilauea

• ArraysArrays

• Observations in Chronological OrderObservations in Chronological Order

– Multiple types of tremorMultiple types of tremor

– Skylight DetectionSkylight Detection

– Two fissure eruptionsTwo fissure eruptions

• Acoustic energy vs. seismic/tilt eventAcoustic energy vs. seismic/tilt event

• ConclusionsConclusions

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Pu`u` O`o Crater Complex

• Pu`u O`o crater complex is the active section of Kilauea VolcanoPu`u O`o crater complex is the active section of Kilauea Volcano

• Nearly continuous effusion and degassing from multiple vent system since 1992Nearly continuous effusion and degassing from multiple vent system since 1992

• Lava flowed from the crater complex ~13 km through a complicated conduit Lava flowed from the crater complex ~13 km through a complicated conduit

system until it met the oceansystem until it met the ocean

• Multiple open vents and lava tube skylights appear activeMultiple open vents and lava tube skylights appear active

• System changed in June 2007 System changed in June 2007 fissure eruptions fissure eruptions

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Infrasound Arrays – MENE

MENE ArrayMENE Array• Semi-permanentSemi-permanent• 12.5 km from Pu`u 12.5 km from Pu`u

O`o O`o • Dense JungleDense Jungle• Since 9/06Since 9/06

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Infrasound Arrays – KIPU

KIPU ArrayKIPU Array• 2 week deployment 2 week deployment

in 4/07in 4/07• 2.5 km from Pu`u 2.5 km from Pu`u

O`o O`o • High S/NHigh S/N• Collocated BB SeisCollocated BB Seis

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ZION ArrayZION Array• Since 9/07Since 9/07• 7 km from Pu`u O`o7 km from Pu`u O`o• 6.5 km from Fissure D6.5 km from Fissure D• Better azimuthal Better azimuthal

resolution resolution • Results preliminaryResults preliminary

STC SeismometerSTC Seismometer

Infrasound Arrays - ZION

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Infrasonic Tremor for 12/1/2006

• Usually constant between Usually constant between ~0.5-3 Hz~0.5-3 Hz

• Harmonic, gliding tremor Harmonic, gliding tremor as wellas well– Broad harmonics (~2 Hz)Broad harmonics (~2 Hz)– High Attenuation?High Attenuation?

• Gliding (spectral peaks change Gliding (spectral peaks change frequency over time)frequency over time)– Magma level may define Magma level may define

effective length of conduiteffective length of conduit

• Seismic spectrogram from Seismic spectrogram from same period has relatively same period has relatively uniform tremor, some uniform tremor, some harmonicsharmonics

• Tremor not visible in Tremor not visible in waveformswaveforms

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KIPU results – Tremor and Skylight

• PMCC Detections:PMCC Detections:4/22/07 1510-1525 4/22/07 1510-1525

• Nearly all signal originated Nearly all signal originated from Pu`u O`o from Pu`u O`o

• Discovered skylight along Discovered skylight along lava tube systemlava tube system– Intermittently acoustic active, Intermittently acoustic active,

both audible and infrasoundboth audible and infrasound

• Possible to discriminate Possible to discriminate between the two sourcesbetween the two sources

• Need confirmation of Need confirmation of detection…detection…

KIPU

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KIPU results – 4/22/07 0600-0800 UTC

• A sharp, complex spectral peak of ~0.6 Hz is present at KIPU and MENEA sharp, complex spectral peak of ~0.6 Hz is present at KIPU and MENE• Tends to bifurcate and shift frequency over timeTends to bifurcate and shift frequency over time• Seismic wavefield is complex and path effects appear to be present, but Seismic wavefield is complex and path effects appear to be present, but

spectral peak is also manifestedspectral peak is also manifested• Broadband infrasound signal as wellBroadband infrasound signal as well

Black-2.5 km inf

Red-13 km inf

Blue-seismic

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Episode 56

• EQ swarm begins EQ swarm begins around 6/17 1415 around 6/17 1415 UTC on upper east rift UTC on upper east rift zone near Mauna Uluzone near Mauna Ulu– Magma intrusion Magma intrusion

1.5-3 km deep1.5-3 km deep

• Puu Oo Vent collapses Puu Oo Vent collapses on 6/18on 6/18

• First impulsive First impulsive acoustic events at acoustic events at Puu OoPuu Oo

• Relatively long Relatively long durationduration

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Episode 56 – Fissure Opening

• Infrasound signals Infrasound signals around 1015-1045 around 1015-1045 UTC from ~132°UTC from ~132°

• Fissure Opening?Fissure Opening?

Fissure Opening?

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Episode 56 - Resuts

• 200 m long fissure opens 6 200 m long fissure opens 6 km west of on 6/19km west of on 6/19– Steam, gas, and lava Steam, gas, and lava

• Infrasound recordings from Infrasound recordings from 0900-1100 UTC pm 6/190900-1100 UTC pm 6/19– Focused between 2-10 Hz, Focused between 2-10 Hz,

doesn’t look like surf or doesn’t look like surf or culturalcultural

– Not constrained well by any Not constrained well by any other technologyother technology

– Harmonics presentHarmonics present– Similar to Puu OoSimilar to Puu Oo

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

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Fissure Eruption- 8/22/07

• Increased tremor Increased tremor signals in late signals in late AugustAugust

• Activation of Activation of harmonics around harmonics around 2000 UTC2000 UTC

• Increased activity Increased activity prompted prompted installation of installation of second array in second array in GlenwoodGlenwood

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Fissure Eruption – 7/21/2007: Single array

• Fissure signal Fissure signal concentrated concentrated between 1.5-5 between 1.5-5 Hz, similar to Hz, similar to Puu OoPuu Oo

• No harmonicsNo harmonics

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ZION Results – 2007/9/17

• Tremor signals Tremor signals switch on to Puu Oo switch on to Puu Oo on 9/17?on 9/17?

• Puu Oo still actively Puu Oo still actively degassingdegassing

• Standing HypothesisStanding Hypothesis– Magma interacting Magma interacting

with the gaswith the gas– Many ways of Many ways of

producing this producing this processprocess

– Want to model Want to model broad spectral broad spectral peakpeak

FD

PO

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Daily Acoustic Energy Calculation

• Calculate acoustic source energy for tremorCalculate acoustic source energy for tremor• To differentiate between signal and noise, the To differentiate between signal and noise, the

acoustic energy is only calculated during times acoustic energy is only calculated during times of coherent signal from the specified azimuth. of coherent signal from the specified azimuth.

• Split data into 60 sec windowsSplit data into 60 sec windows• Mean correlation value for window must be Mean correlation value for window must be

above thresholdabove threshold• Minimum number of pixels per windowMinimum number of pixels per window

Fissure Eruptions

EAcoustic=2πr2/ρc ∫ΔP(t)2dt

r=source-receiver distance

ρ=air density

C=sound speed

ΔP=change in pressure

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Acoustic Energy vs. RSAM/Tilt

• Event 1: 8/24 00:02 UTC (8/23 14:02 HST) Event 1: 8/24 00:02 UTC (8/23 14:02 HST) • Collapse Event: Collapse Event:

– Significant drop-off in acoustic energy (tremor) in the days following this collapse Significant drop-off in acoustic energy (tremor) in the days following this collapse event. event.

– Event preceded by 3 days of high acoustic tremor and RSAM values. 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 No impulsive acoustic signal recorded at the time of the seismic/tilt event. Minor

earthquake recorded by the infrasound sensors around 0000 UTC. earthquake recorded by the infrasound sensors around 0000 UTC. – Collapse event may have changed magma/degassing dynamics. Collapse event may have changed magma/degassing dynamics.

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Acoustic Energy vs. RSAM/Tilt

• Event 2: 8/29 1100-1400 UTC (8/29 0100-0400 HST) Event 2: 8/29 1100-1400 UTC (8/29 0100-0400 HST) • Tremor EventTremor Event

– Strong acoustic and seismic tremor during this 3 hour time period, originating Strong acoustic and seismic tremor during this 3 hour time period, originating from P‘u‘u ‘O‘o, not Fissure D. from P‘u‘u ‘O‘o, not Fissure D.

– Infrasound signal concentrated between 1220-1400 UTC, is below 3 Hz, Collapse Infrasound signal concentrated between 1220-1400 UTC, is below 3 Hz, Collapse event may have changed magma/degassing dynamics. event may have changed magma/degassing dynamics.

– Infrasound signal decreased rapidly at 1400 UTC and returns to similar azimuth Infrasound signal decreased rapidly at 1400 UTC and returns to similar azimuth as Fissure D. as Fissure D.

– No longer-term variation in acoustic energy or RSAM apparent. No longer-term variation in acoustic energy or RSAM apparent. – Similar “burst” of tremor occurred on 9/17 around 0900 UTC. Similar “burst” of tremor occurred on 9/17 around 0900 UTC.

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Acoustic Energy vs. RSAM/Tilt

• Event 3: 9/3 0152 UTC (9/2 1552 HST) Event 3: 9/3 0152 UTC (9/2 1552 HST) • Collapse Event:Collapse Event:

– Nothing out of the ordinary recorded acoustically at the time of this collapse Nothing out of the ordinary recorded acoustically at the time of this collapse event. event.

– However, tremor energy levels decreased to near zero in the days following. However, tremor energy levels decreased to near zero in the days following. Collapse event may have changed dynamics as well.Collapse event may have changed dynamics as well.

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Conclusions – Future Work

• Identification of new sources (skylight, fissures) made at Kilauea Identification of new sources (skylight, fissures) made at Kilauea

• Tremor observations consistent with pressure oscillations resulting Tremor observations consistent with pressure oscillations resulting from unsteady magma flow within tubes/conduitsfrom unsteady magma flow within tubes/conduits

• P‘u‘u ‘O‘o tremor between 0.5 – 3 Hz fairly constant in both P‘u‘u ‘O‘o tremor between 0.5 – 3 Hz fairly constant in both infrasound and seismic recordings before 6/18infrasound and seismic recordings before 6/18

• Higher frequency harmonic, gliding tremor more intermittent and Higher frequency harmonic, gliding tremor more intermittent and possibly due to excitation of conduitpossibly due to excitation of conduit

• Sharp spectral peaks in infrasound and seismic – same resonating Sharp spectral peaks in infrasound and seismic – same resonating source?source?

• Comparison of seismic, infrasound, and tilt data help explain Comparison of seismic, infrasound, and tilt data help explain dynamics and overall volcanic activity levelsdynamics and overall volcanic activity levels