Global Infrasound Monitoring

1
Global Infrasound Monitoring Research and
Applications

• Henry E. Bass, Carrick Talmadge, and Kenneth
  Gilbert, National Center For Physical Acoustics,
  University of Mississippi
• Michael Hedlin, Gerald DSpain, and Jon Berger,
  Scripps Institution of Oceanography, University
  of California San Diego
• Milton Garces and Claus Hetzer, ISLA, University
  of Hawaii
• John V. Olson, Charles Wilson, Curt Szuberla and
  Daniel Osborne, University of Alaska at Fairbanks
• Paul Golden and Gene Herrin, Southern Methodist
  University
• Richard Kromer and Pres Herrington, Sandia
  National Laboratory
• Rod Whitaker and Doug Revelle, Los Alamos
  National Laboratory
• Keith McLaughlin, Joydeep Bhattacharyya, Bob
  Woodward and Bob North, SMDC Monitoring Research,
  Arlington, VA
• David Norris and Rob Gibson, BBN Technologies,
  Arlington, VA

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Research Issues

• Use of Infrasound Data to Further other Research
• Hazard Warning
• Meteorology
• Sprite Physics
• Bolide Distributions
• Research Needed to Optimize Infrasound Station
  Performance
• Wind Noise Reduction
• Signal Processing Techniques and Processes
• Research Needed to Optimize Use of Data
• Source Characterization
• Meteorological Effects

3
GE Earthquakes, Tsunamis, Avalanches

• Civil Disaster Management

LePichon, 2001 Arequipa Earthquake June 23, 2001
Mb 4.3 at IS59
4
GE Volcanoes

• Eruption and ash monitoring
• Eruption forecasting
• Atmospheric tomography

IS59 Kilauea, Mauna Loa, and Hualalai, Hawaii
Hekla, Iceland (Lizska, 2001)
IS55 Erebus, Antarctica
LePichon, 2001 Etna, Italy
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GE Severe Weather

• Microbaroms may allow storm tracking with
  infrasound

Microbaroms and surf (800x)
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Meteorological Effects

• Speed of Sound Varies With Altitude, Location and
  Time
• Current Meteorological Models and Limitations
• Propagation Models/Verification
• Tomography

7
The Speed of Sound is Determined by Wind Speed
and Temperature
8
GE Electromagnetic Activity

• Sprites, Aurora

source at 90 km height
Liszka, 2001 Sprites in Sweden May 26/27, 1995
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GE Bolides

• Bolide impact distribution will be modified by
  new infrasonic recordings get stats!

2001 Leonid recorded at IS59
April 23, 2001 10kt
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GE Turbulence and Atmospheric Waves

• Clear air turbulence monitoring
• Lower, middle and upper atmosphere dynamics

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GE Littoral Processes
Kualanui 100X
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Microbarams

• Progress towards predicting amplitude and
  frequency dependence not just existence.

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• Coastal surf activity

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Geophysical Events IS10
Brown, 2000, in McCormack, 2001
N
IS10 Winnipeg, Canada December 16, 1999 to
September 1, 2000 Approximately 4200
detections
microbaroms, Hudson Bay ?
Local blasting, Too small to register on local
seismic
?
E
W
Local blasting Thunder Bay area, too small to
register on local seismic
mining activity, Minnesota, registers strongly on
local seismic
microbaroms, Pacific Ocean (?)
S
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Geophysical Events

• Ground Truth Event Database is growing CMR and
  IDC
• Some sources are poorly characterized

Subset of CMR GT Database
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Source Characterization

• Explosions
• Weather
• Lightning
• Volcanoes
• Bolides
• Earthquakes, Tsunamis, etc.

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Research Needed to Optimize Infrasound Station
Performance

• Wind Noise
• Infrasonic Wave Propagation
• Sensors and calibrators

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Wind Noise
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Wind-noise-reducing filters

• 120-port design
• Valves at each port and at main manifold
• PVC construction
• Custom manifolds, off-the-shelf fittings
• Fenced area

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Alternatives to Spatial Filtering

• OFIS Still filters spatially but sums at the
  speed of light.
• Microphone Arrays Still filters spatially but
  sums at the speed of light.
• Active wind noise correction.

21
SI Infrasonic Wave Propagation

• Some progress in integration of required
  environmental information for modeling further
  work required to resolve outstanding issues such
  as
• observed errors in azimuth
• phase identification
• scattering and diffraction
• Final goal of an operational full modeling
  capability (waveforms, travel times, phase
  velocities, amplitudes)
• Continue to collect ground truth data and
  associated environmental information

22
SI Sensors and calibrators

• A number of new sensor technologies are under
  development
• Global network should continue to take advantage
  of innovations in infrasound technology
• Need for field calibrators and calibration
  standards
• Development of new sensor types should consider
  calibration requirements

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Concluding Remarks

• Keep in mind that we do not understand most
  signals received what are we missing?
• We might be keen on improving our stations but
  the true value is in the information provided
  about physics of interest not the station per
  se.
• Hazard Warning is a Hot Topic but Hot Topics
  change good physics remains good physics.

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The End