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CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound Data Processing into IDC OperationsPresented at: Infrasound Technology Workshop in Bermuda 3-7 November 2008
Nicolas Brachet, Pierrick Mialle, David Brown and John Coyne
Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty OrganizationProvisional Technical Secretariat / International Data CentreVienna International CentreP.O. Box 1200A-1400 ViennaAUSTRIA
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Outline of Presentation
Final preparation for moving infrasound into operations
Tuning the automatic infrasound processingDetection/detection categorization/phase association
Interactive review of infrasound signals
Enhancement of the automatic infrasound processing
Station Noise characterization & Amplitude computation(cf. David Brown’s presentation)
Atmospheric modeling (atm. specifications & simulation tools)
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return ofInfrasound in IDC Operations
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsMilestones
Historical Operational Milestones
• September 2003: Guidelines from CTBT/WGB/TL-2/79“Significant effort should be directed into assessment and further development of infrasound tools for analysis. It is recognized that some existing tools (e.g. PMCC) show considerable potential for forming the basis for infrasound analysis, but are not yet in a form suitable for routine operations.”
• March 2004: Infrasound are temporarily disconnected from network processing until a solution is found to reduce the number of (bogus) infrasound events in the IDC automatic bulletins.
• July 2004: DFX-PMCC installed in Operations
• November 2004: Detection categorization installed in Operations
• July 2007: Interactive infrasound review tool (ARS-Geotool-PMCC) in Operations
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsMilestones
And also offline development & testing work …• 2006: Use of frequency-distance attenuation curve to reduce the number of false associations of infrasound detections
• 2007: Preliminary analyst procedure & guidelines for saving infrasound events (selected infra started to be added to REB)
• Ongoing: Enhancement of existing automatic and interactive software …
Accomplishments in 2008• New functions implemented in Geotool-PMCC interactive review tool
• Prepare DFX-PMCC low frequency configuration for Solaris/Linux
• Tune detection categorization
• Work on Station Noise characterization & Amplitude computation
• Tune GA to reduce the number of false associations with infra detections
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Low frequency DFX-PMCC for Solaris (and Linux)• Objective: Enhanced detection capability, especially for distant events
• Processing frequency bands between 0.07 and 4.0 Hz
• Acceptable CPU time for Solaris machines (IDC Operations): Use of 11 frequency bands and duration of cross correlation windows between 30 and 60 seconds
• Validation of the new detector configuration using the IRED*
Example from IRED: Kasatochi eruption on August 8, 2008 detected at I22FR (New Caledonia), distance=8410km, signal frequency<0.1Hz
*IDC Infrasound Reference Event Database
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Tuning of DFX-PMCC for oceanic infrasound stations(I04AU, I05AU, I13CL, I14CL, I18DK, I27DE, I36NZ, I52GB, I55US)
• Objective: Reduce the oversensitivity of DFX-PMCC to local ocean surf noise
• IMS array configuration including very small aperture sub-arrays (~100m) may not be optimum for seaside areas
1.5km
80m
Robinson Crusoe I14CL
130m
110m
80m
Inner sub-array at I14CL
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Tuning of DFX-PMCC for oceanic infrasound stations (cont.)
Action
• Do not start DFX-PMCC processing with too small inner triplet configuration
or/and
• Increase the required minimum number of detecting elements in an array to ensure distant elements also contribute to the final detection solution.
Inner sub-array at I14CL
200m
180m
160m
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Before tuning131 detections related to surfand microbaroms
After tuning74 detections related to surfand microbaroms
Results: The number of detections due to ocean surf decreased, with more stable detection attributes (back azimuth/trace velocity values)
Example of I13CL (Easter Island), 26 October 2008 period 00:00-04:00UTC
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Tuning of network processing (GA)• Objective: reduce the number of false automatic associations with infra detections to a manageable level for analyst review (~10 to 15 automatic events per day)
• Set up a testing/review environment (development LAN/InfraNet) and elaborate new infrasound criteria for GA
All SHI events
SHI eventsusing new
criteria
Review signal detections & events
Geotool-PMCC IRED
Database
InfraNet
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Tuning of network processing (cont.)• Positive criteria: retain only certain types of infrasound associations
Large events: Events built with a minimum of arrivals from 3 primary stations (infra + eventually seismic), provided the first detected infrasound arrival is within 40 deg. Seismic events: Events built with at least 1 seismic phase detected on infra station (+ seismic phases on seismic stations) Significant events: Events including at least 1 significant infra detection (Cfreq between 0.4 Hz and 2.5 Hz ; family size>20 pixels ; family duration>120s), provided the first detected infrasound arrival is within 40 deg
• Negative criteria: Give zero weight to very small low frequency infrasound detections (Cfreq<0.25Hz and family size<12 pixels) and reject events with less than 2 primary stations
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Tuning of network processing (cont.)• Current statistics (on development LAN) with 37 operating infra arrays
Daily average:
- 179 SEL3 events(SHI)
- 45 “infra” events before GA criteria
- 17 “infra” events after GA criteria (min. 5, max. 32)
Before criteria After criteria
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC OpsTuning of the Automatic Processing
Tuning of network processing (cont.)• Interactive review of the remaining automatic “infra” events after GA criteria
Comments: • The automatic bulletin contains ~1 valid event per day (usually including only 1 infra station), • Some possible events could not be validated (built with 2 infra stations), • The number of events built with infra stations decreases during week-ends (when there are fewer large detections related to human activity)
Week-ends
Dat
abas
e pr
oble
m
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC Ops Interactive review of infrasound signals
More functional interactive review tool for infrasound data (update of Geotool-PMCC)
Detection background at the station(24 hour summary)
Expandable panel for detection pixels(Azimuth, speed, consistency, correlation, RMS amplitude, number of detecting sensors, F-stats)
Automatic/Manual beam forming
Linear/Log frequency scale
Various polar plots
Wind
frequency
Time
Azimuth
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infrasound processing:
Atmospheric modeling
- Models and tools -
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processingAtmospheric models available at the IDC
Zonal winds at latitude 49N2 March 2007 @15:00 GMT
G2S-ECMWFHWM93
=
0
40
80
120
160
latest HWM07(Drob et al.,2008)
in progress…=
G2S-ECMWF
0
40
80
120
160
0
40
80
120
160
+
ECMWF
0
40
80
120
160
Alt
itud
e (k
m)
Longitude
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processingAtmospheric models available at the IDC
G2S-ECMWFHWM93
HWM07
Meridional winds at latitude 49N2 March 2007 @15:00 GMT
+
=
in progress…=
G2S-ECMWF
0
40
80
120
160
0
40
80
120
160
0
40
80
120
160
ECMWF
0
40
80
120
160
Alt
itud
e (k
m)
Longitude
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processingAtmospheric modeling: Tools
New tools for infra atmospheric modeling at the IDC• Application for producing G2S-ECMWF models (Drob,2007) has been ported
to 64 bit Linux• In June 2008, the IDC received a new software (WASP-3D sph.*, Virieux et
al.) for simulation of infrasound wave propagation in a complex heterogeneous medium
• WASP-3D has been enhanced in order to integrate real-time atmospheric variability (ECMWF data) and recent wind model (HWM07)
• WASP-3D should help better understand the atmospheric propagation and be used at the IDC for comparison with other tools (e.g. Taupc, InfraMAP)
Distance (km)
Tra
velt
imes
(s
)
200
800
1400
240 300 360
I26D
E
0Source
I26DE
Alt
itud
e (k
m)
150
75
0.46
VT
(km/s)
0.36
*Windy Atmospheric Sonic Propagation 3D in Spherical Coordinates
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Novaky explosion (Slovakia), 2 March 2007 @ 15:28:04 GMT
Enhancement of the automatic infra processingAtmospheric modeling: Case study (IRED)
Slovakia
Hungary
Czech Rep.Poland
Austria
IS26IS31
IS46
VRAC
GERES
4500 km
2825 km
IS46IS31
Novaky
Explosion
4 km
REB
Event location refined by analysts REB Location is 5km from GT
SEL3 event built with 3 Infra+1 Seismic arraysAutomatic location 75km from Ground Truth
Source: EMSC and P.Labak
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processingAtmospheric modeling: Case study (IRED)
I26DE (350 km) I31KZ (2825 km) I46RU (4500 km)
Novaky explosion, Waveforms and DFX-PMCC detections
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processingAtmospheric modeling: Case study (IRED)
Novaky explosion, WASP-3D ray tracing at I26DE using different atm. models
HWM93
HWM07
G2S-ECMWF
I26DERay tracing (color=shooting angle) Travel time curves (color=Trace velocity)
I26DE100km
100km
100km
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processingAtmospheric modeling: Case study (IRED)
Novaky explosion, WASP-3D ray tracing at I31KZ using different atm. models
HWM93
HWM07
Only stratospheric rays are displayed It branches
Is branches
G2S-ECMWF
I31KZ
I31KZ
50km
50km
50km
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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I26DE I31KZ I46RU
DFX-PMCCCel. (m/s) 256 307 305
∆Az (deg.) 0.54 0.91 1.85
Atm. models HWM93G2S-
ECMWFHWM07 HWM93
G2S-ECMWF
HWM07 HWM93G2S-
ECMWFHWM07
Taupc
Cel. (m/s)
234 303 309
∆Az (deg.)
0.85 -0.6 -1.0
WASP-3D Sph
Cel. (m/s)
235 238 235 304-312 303-308 299-304 295-300 300-304 295-301
∆Az (deg.)
1.2 1.1 1.0 1.55-1.8 0.95-1.35 0.7-1.4 3.5-4.0 3.0-3.2 1.75-2.1
Enhancement of the automatic infra processingAtmospheric modeling: Case study (IRED)
Novaky explosion, Summary of ray tracing results (observed/predicted celerity and back az. deviation)
CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Summary
Pre-requisite for moving infrasound into IDC Operations Tuning the automatic infrasound processing to reduce the number of bogus
infrasound events down to a manageable level for analyst interactive review (~15 automatic infrasound events/day)
Suitable tool for Interactive review of infrasound signals Analyst procedure & guidelines for building infrasound events Scheduled re-introduction of infrasound into Operations (beginning of 2009)
Enhancement of the automatic infrasound processingNew acquisitions at the IDC in 2008 for atmospheric modeling Atmospheric specifications: HWM2007, integration to G2S-ECMWF in progress Simulation tool: WASP-3D ray tracing
Encouraging results, need for intensive testing and validation of the new models and tools on reference events (IRED)