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Recent developments on infrasound data
processing at the French NDC
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• Review of data processing
• Automatic processing detection using PMCC,
  bulletin edition
• Geophysical monitoring by use of meteorological
  data
• Use of realistic propagation models for source
  location
• Valid for long propagation range
• Analysis of the Alaska earthquake
• Recent experiment on fusion of I bulletins
• Event definition
• Clustering and identification event bulletin
• Source location procedure
• Some results

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Real time processing of infrasonic data
Raw data station IS
Automatic data processing PMCC wind noise
control
Automatic bulletin 0.02-4 Hz
Detection screening Recordings detections
Interactive processing on selected waveforms
WinPmcc
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Analyst review Waveforms and detection screening
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I17CI Ivory-Coast
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I34MN Wind-noise evaluation
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I17CI Wind-noise effect on the detectability

• Explain the decrease of detection number during
  windy periods
• Identification of false detections
• ? meteorological data are stored for each
  detection

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50
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Use of 3D infrasound modeling by ray-theory in
moving medium WASP-3D
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Infrasound generated by the M7.9 Alaska
earthquake
Pmcc detection at I10CA - 3370 km
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G2S atmospheric profiles
I10CA
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Time/range dependent propagation models

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F
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Location of secondary sources with G2S winds
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Studies on sources location Automatic
fusion of I bulletins Flers - I26DE / DBN
Context - Distance between stations 1000
km - Station configuration similar
aperture - Data availability over one month
period - Existence of known sources -
Same processing methods and parameters
Objectives - Development of location
procedures including realistic propagation
modeling - Consider the event definition
- Development of clustering methods to remove
long duration phenomena ? Reduce the number
of fortuitous associations
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Event definition
AF Concorde one event
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(No Transcript)
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Location procedure
Exclusion principle One event cannot participate
to more than one location Uniqueness principle
One source cannot generate more than one event
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Location results

• After clustering and
• removing
• 76 localizations / 8945 detections
• ? 92 of non associated detections
• Identified events 67
• Others fortuitous associations lt 33

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Billy-Berclau explosion March 27, 2003
http//www.knmi.nl/evers/infrasound/events/030327
/billy-berclau.html
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Others ...
Flers - 714 km
DBN - 1180 km cel 0.29 km/s q / qtho 204 /
207
I26DE - 1365 km
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Summary

• Simultaneous analyses of background noise,
  meteorological data and detection results are
  beneficial
• High variability of the propagation conditions
  need for realistic time/range dependent modeling
• Large number of local events / need for station
  signatures based on a detailed knowledge of the
  local environment
• Clustering methods should be addressed to tag /
  remove long duration phenomena (MAW / microbaroms
  / surf noise )