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Evaluation of the ASHE Project, Ecuador

Comprehensive evaluation of the ASHE project in Ecuador, focusing on geophysical infrasound sources detected, energy estimates, volcanic signals analysis, and eruption monitoring techniques.

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Evaluation of the ASHE Project, Ecuador

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  1. Evaluation of the ASHE Project, Ecuador M. Garcés1, D. Fee1, and A. Steffke1 D. McCormack2 and R. Servranckx3 H. Bass4 and C. Hetzer4 M. Hedlin5 and R. Matoza5 H. Yepes6 and P. Ramon6 1Infrasound Laboratory, University of Hawaii at Manoa 2Geological Survey of Canada, 1 Observatory Crescent, Ottawa K1A 0Y3 Ontario, Canada 3Montréal Volcanic Ash Advisory Centre, Canadian Meteorological Centre, Meteorological Service of Canada 4University of Mississippi 5University of California, San Diego 6Instituto Geofísico, Escuela Politécnica Nacional,Quito, Ecuador ITW, Bermuda, 2008

  2. Efficient Geophysical Infrasound Sources Routinely Detected by IMS Bolides – low mass, hypersonic (10’s of km/s) short duration, broad band, moving source(s) distributed in space (line) Microbaroms - high mass (moving swaths of ocean), low velocity (m/s), nearly continuous, narrow band, multiple moving sources distributed in space (areas). Surf – medium mass, low velocity (10’s m/s), sustained over periods of days, broadband, multiple moving sources distributed over coastal areas. Volcanoes – high mass (erupted volumes of cubic km), medium to high speeds (up to ~Mach 1), impulsive to continuous durations, narrow and broadband signals, well localized surface source (point). Stationary in space, but very nonstationary in time. Due to substantially different physics, energy estimates for ocean and volcanic processes do not lend themselves well to equivalent yield scaling. Propose use of Watts and Joules for continuous and impulsive events, respectively. Well suited energy units for comparison with satellite methodologies. Acoustic to electrical energy efficiency for speakers is typically ~1-10%.

  3. Volcanosonic signals TRANSIENTS: Explosions - impulsive, bipolar pulses with durations of seconds. Long Period events - possibly emergent events sustained for seconds to minutes. Spectral peaks in 0.5-5 Hz band. Very Long Period Events - pulses in the 0.5 – 0.001 Hz band TREMOR/JETTING: Near continuous oscillation sustained for minutes to years.

  4. Galeras ASHE EcuadorInstrumentation LITE Reventador Ecuador Tungurahua RIOE RIOE Tungurahua: 37 km LITE Tungurahua: 251 km Sangay MACE

  5. Time period: 2/15/06- Fall 08 • Automatically calculate azimuth, amplitude, duration, and acoustic energy • >20,000 explosions at RIOE (37 km) • >3500 explosions at LITE (251 km) • High-pass filter data >.5 Hz • STA/LTA  event onset and end time • 2/5 secs, 3/40 secs • Detection must be on all 4 channels • Run PMCC between 0.5-4 Hz • 10 bands, 10 sec windows • Families with correct azimuth (±7°) • Minimum family size and amplitude Automatic explosive event identification

  6. Explosions Range of 5 km, 40 km, and 250 km. Near field data courtesy of Kumagai and Molina, 2008

  7. No obvious cutoff amplitude • Picked up everything over 0.7 Pa, but missed a few around 0.6 while picking up some as small as 0.2 Pa • Detection may depend on local noise and high-altitude wind Localization Using thermospheric arrivals for LITE and direct path for RIOE mean error (km) = 2.5518 Mean delta lat = 0.0086 Mean delta lon = -0.0051 Diffraction zone! Using stratospheric arrivals for LITE and direct path for RIOE Mean error (km) = 6.7821 Mean delta lat = 0.0534 Mean delta lon = 0.0281

  8. Main Eruption: 1930-0620 UTC Total Duration ~10.8 hours • VEI 4 eruption inferred from satellite estimate of ash height • >20 pyroclastic flows and up to 6 km lava fountain! • Intense jetting (±5 Pa at 37 km) • Ejection of dark, ~24-km high, ash-laden plume. Case Study: 8/16-17 2006

  9. System Training: Case Study of 8/16-17 2006 Growing list of case studies compare satellite-derived ash heights with acoustic signal intensity and character derived from arrays. Used fine-scale atmospheric specifications typically used for sound propagation studies.

  10. System Training: Case Study of 8/16-17 2006 Spectrogram for the Plinian phase of the 8/16 eruption. Note the increase in energy and decrease in frequency of the signal around 0530 UTC. The frequency axis is plotted on a logarithmic scale.

  11. Training Set: Tungurahua Eruption PSDs

  12. Automatically posted on web page • Free Space Acoustic Energy: • EAcoustic=2πr2/ρc ∫ΔP(t)2dt • r=source-receiver distance • ρ=air density • c=sound speed • ΔP=change in pressure • Acoustic power = Energy/time • To minimize the effects of wind noise, the acoustic energy was calculated above 0.5 Hz (reprocessed above 0.1 Hz for some signals) • Acoustic energy only calculated if PMCC results corresponded to significant acoustic signal arriving from ±7° of Tungurahua Sustained Signal Identification and Monitoring

  13. Spectrogram, Acoustic Source Power, and Ash Cloud Height Ops: Automatic Eruption Notification of 2/6/08 Used coarse atmosphere ASHE Activity Notification ASHE Explosion Notification 5-minute notification latency!

  14. Okmok and Kasatochi Detections by IMS stations: Latency of ~1h/1000 km (precedent: Anatahan, Chaiten) Kasatochi

  15. ASHE system demonstrated capability to reliably monitor volcanoes at regional distances, with an automatic eruption notification latency of 5 minutes or less for arrays deployed within 40 km. Although sufficiently mature, in the US this technology is not yet integrated into operational environments. • Global Infrasound Network capable of detecting large eruptions with a latency of ~1h/1000 km. New global study will be initiated by ASHE team in Winter 2008. • Future research on propagation studies, correlating ash emissions with different type of infrasonic signals, and a more complete understanding of jet noise. Extend existing detection and notification algorithms to other volcanic environments. Evolution and refinement of notification thresholds. • Recommendations of the 4th Meeting of the International Airways Volcano Watch Operations Group, Paris, France 15-19 September 2008: That VAACs Montreal, Washington and Toulouse a) Continue to assess the feasability of using infrasound data to automatically identify ash producing volcanic eruptions b) prepare a report in time for consideration by the IAVWOPSG-5 Meeting (March 2010). Summary & Next Steps

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