Evaluation of the ASHE Project, Ecuador M. Garcés 1, D. Fee 1, and A. Steffke 1 D. McCormack 2 and R. Servranckx 3 H. Bass 4 and C. Hetzer 4 M. Hedlin 5 and R. Matoza 5 H. Yepes 6 and P. Ramon 6 1 Infrasound Laboratory, University of Hawaii at Manoa 2 Geological Survey of Canada, 1 Observatory Crescent, Ottawa K1A 0Y3 Ontario, Canada 3 Montréal Volcanic Ash Advisory Centre, Canadian Meteorological Centre, Meteorological Service of Canada 4 University of Mississippi 5 University of California, San Diego 6 Instituto Geofísico, Escuela Politécnica Nacional,Quito, Ecuador ITW, Bermuda, 2008

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%. Efficient Geophysical Infrasound Sources Routinely Detected by IMS

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

ASHE Ecuador Instrumentation RIOE LITE MACE Sangay Tungurahua Reventador Galeras Ecuador RIOE  Tungurahua: 37 km LITE  Tungurahua: 251 km

Automatic explosive event identification 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 Hz 10 bands, 10 sec windows Families with correct azimuth (±7°) Minimum family size and amplitude

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

Localization 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 Using thermospheric arrivals for LITE and direct path for RIOE mean error (km) = Mean delta lat = Mean delta lon = Using stratospheric arrivals for LITE and direct path for RIOE Mean error (km) = Mean delta lat = Mean delta lon = Diffraction zone!

Case Study: 8/ Main Eruption: 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.

System Training: Case Study of 8/ 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.

System Training: Case Study of 8/ 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.

Training Set: Tungurahua Eruption PSDs

Sustained Signal Identification and Monitoring Automatically posted on web page Free Space Acoustic Energy: E Acoustic =2πr 2 /ρc ∫ΔP(t) 2 dt 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

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

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

Summary & Next Steps 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 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 4 th Meeting of the International Airways Volcano Watch Operations Group, Paris, France 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).