IMS Infrasound Station Observations of the Recent Explosive Eruptions of Okmok and Kasatochi Volcanoes, Alaska. J. V. Olson, K. Arnoult, C. A. L. Szuberla, C. Wilson Wilson Infrasound Observatory, Geophysical Institute, University of Alaska Fairbanks, M. Garces ISLA, University of Hawaii, - PowerPoint PPT Presentation
IMS Infrasound Station Observations of the Recent Explosive Eruptions of Okmok and Kasatochi Volcanoes, Alaska J. V. Olson, K. Arnoult, C. A. L. Szuberla, C. Wilson Wilson Infrasound Observatory, Geophysical Institute, University of Alaska Fairbanks, M. Garces ISLA, University of Hawaii, M. Hedlin, L2A, IGPP, University of California, San Diego S. McNutt Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks Presented at the 2008 International Technical Workshop, Bermuda
Transcript
IMS Infrasound Station Observationsof the Recent Explosive Eruptions
of Okmok and Kasatochi Volcanoes, Alaska
J. V. Olson, K. Arnoult, C. A. L. Szuberla, C. WilsonWilson Infrasound Observatory, Geophysical Institute, University of Alaska
Fairbanks,
M. GarcesISLA, University of Hawaii,
M. Hedlin,L2A, IGPP, University of California, San Diego
S. McNuttAlaska Volcano Observatory, Geophysical Institute, University of Alaska
Fairbanks
Presented at the 2008 International Technical Workshop, Bermuda
• five major explosive eruptions• beginning ~22:00 UT, 7 Aug• ending ~04:35 UT, 8 Aug• ash emissions became continuous after these events reaching altitudes > 35,000 ft asl
Okmok volcano• 53.397N, 168.166W• Eruption time:
• Explosion: 12 July 08, 19:43 UT with continuing ash emissions• ash cloud top 30-35,000 ft asl
ITW Workshop, Bermuda 2008
Eruption Details at at www.avo.alaska.edu
Kasatochi, 17:00 UT, 8 Aug 08Photo by JT Ford
Kasatochi
Great circle distances to US IMS stations Kasatochi Expected Travel Time
The MCCM detector along with the least-squares estimates of azimuth, velocity and the residuals (στ) are computed using a sliding window 500 sec long, updated every 50 sec
ITW Workshop, Bermuda 2008
Kasatochi: Detections (1)Pure-State Data
I18Azimuth: 299.9o
Trace velocity: m/sec
I10Azimuth: 304.8o
Trace velocity: m/sec
ITW Workshop, Bermuda 2008
Kasatochi: Detections (2)Pure-State Data
I56Azimuth: 300o
Trace velocity: 374 m/sec
I53Azimuth: 244o
Trace velocity: 358 m/sec
ITW Workshop, Bermuda 2008
Kasatochi: Detections (3)Pure-State Data
I57No signal found
I59Azimuth: 336o
Trace velocity: 312 m/sec
ITW Workshop, Bermuda 2008
Kasatochi: Detections (4)Pure-State Data
I30Azimuth: 47.8o
Trace velocity: 370 m/sec
ITW Workshop, Bermuda 2008
Kasatochi Simple Back Azimuth Location
I53
I56
I59
K
Simple back-azimuth projections along the great-circle between IMS stations results in an average location that is approximately 200 km Southwest of Kasatochi and encompasses a region several hundred km wide.
I30
I18
I10
K
ITW Workshop, Bermuda 2008
IMSArray
Azimuth(o)
GC Dist (km)
I53 241.38 1706
I30 46.6 4439
I59 347.3 3903
I56 298.8 3548
I18 294.1 4464
I57 314.8 4583
I10 303.3 4754
I34 49.7 5688
I34
I30O
I59
I53
I56I57
I10
I18
Okmok – IMS Arrays(within ~6000 km)
ITW Workshop, Bermuda 2008
Okmok Waveforms (1)I53, I56
ITW Workshop, Bermuda 2008
Okmok Waveforms (2)I57, I59
ITW Workshop, Bermuda 2008
Okmok: Detections (1)Pure-State Data
I53Azimuth: 236o
Trace velocity: 360 m/sec
No signal found
ITW Workshop, Bermuda 2008
Okmok: Detections (2)Pure-State Data
No signal found
ITW Workshop, Bermuda 2008
Summary
• Both eruptions were strong, exposive eruptions lasting several hours and producing extensive ash plumes
• Kasatochi:– Amplitudes ~1Pa observed at distances to 4000 km– Simple great-circle back-azimuths give a location
~200 km Southwest of the source• Okmok:
– Observed only at I53US, amplitudes ~0.01 – 0.1 Pa• We are collecting atmospheric data:
– Effects of wind– Estimate signal paths through time delays
