Preparing the Return of Infrasound
Data Processing into IDC Operations
Presented 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 Organization
Provisional Technical Secretariat / International Data Centre
Vienna International Centre
P.O. Box 1200
A-1400 Vienna
AUSTRIA
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 processing
Detection/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 of
Infrasound 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 Ops
Milestones
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 Ops
Milestones
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
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Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC Ops
Tuning 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 Ops
Tuning 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
80m
130m
110m
1.5km
80m
Robinson Crusoe I14CL
Inner sub-array at I14CL
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Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC Ops
Tuning 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.
CTBTO/IDC
Inner sub-array at I14CL
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC Ops
Tuning of the Automatic Processing
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
Before tuning
After tuning
131 detections related to surf
and microbaroms
74 detections related to surf
and microbaroms
CTBTO/IDC
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Preparing the Return of Infrasound in IDC Ops
Tuning 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
Database
Review signal detections & events
All SHI events
SHI events
using new
criteria
InfraNet
CTBTO/IDC
Geotool-PMCC
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
IRED
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Preparing the Return of Infrasound in IDC Ops
Tuning 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 Ops
Tuning of the Automatic Processing
Tuning of network processing (cont.)
• Current statistics (on development LAN) with 37 operating infra arrays
Daily average:
Automatic SEL3 events
250
- 179 SEL3 events
(SHI)
200
150
- 45 “infra” events
before GA criteria
100
50
Total SHI
CTBTO/IDC
no criteria
Before
criteria
28-Oct
27-Oct
26-Oct
25-Oct
24-Oct
23-Oct
22-Oct
21-Oct
20-Oct
19-Oct
18-Oct
17-Oct
16-Oct
15-Oct
14-Oct
13-Oct
12-Oct
11-Oct
10-Oct
09-Oct
08-Oct
07-Oct
06-Oct
05-Oct
04-Oct
03-Oct
02-Oct
01-Oct
30-Sep
0
with criteria
criteria
After
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
- 17 “infra” events
after GA criteria
(min. 5, max. 32)
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Preparing the Return of Infrasound in IDC Ops
Tuning of the Automatic Processing
Tuning of network processing (cont.)
• Interactive review of the remaining automatic “infra” events after GA criteria
Database problem
Possible
events
14 (8%)
Validated
events
9 (5%)
Rejected
events
150
(87%)
Reviewed "infra" events
Week-ends
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)
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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)
Linear/Log
frequency scale
Expandable panel for detection pixels
(Azimuth, speed, consistency,
correlation, RMS amplitude, number of
detecting sensors, F-stats)
Azimuth
Various polar plots
frequency
Time
Wind
Automatic/Manual
beam forming
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 processing
Atmospheric models available at the IDC
HWM93
Zonal winds at latitude 49N
2 March 2007 @15:00 GMT
160
160
120
120
ECMWF
80
Altitude (km)
160
120
+
80
G2S-ECMWF
=
80
40
40
0
0
160
40
G2S-ECMWF
120
0
80
Longitude
=
40
in progress…
latest HWM07
(Drob et al.,2008)
CTBTO/IDC
0
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processing
Atmospheric models available at the IDC
HWM93
Meridional winds at latitude 49N
2 March 2007 @15:00 GMT
ECMWF
160
160
120
120
80
160
Altitude (km)
G2S-ECMWF
=
80
40
40
0
0
120
+
80
160
40
G2S-ECMWF
120
0
80
Longitude
=
40
HWM07
CTBTO/IDC
in progress…
0
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processing
Atmospheric 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)
Altitude (km)
Traveltimes (s)
150
75
0
Source
CTBTO/IDC
VT
Atmospheric Sonic Propagation 3D in Spherical Coordinates
I26DE
(km/s)
200
0.46
I26DE
*Windy
800
0.36
1400
240
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
300 Distance (km)
360
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Enhancement of the automatic infra processing
Atmospheric modeling: Case study (IRED)
Novaky explosion (Slovakia), 2 March 2007 @ 15:28:04 GMT
Poland
Czech Rep.
IS46
IS3
1
Slovakia
Explosion
REB
Austria
Hungary
Source: EMSC and P.Labak
4500 km
VRAC
GERES
IS46
2825 km
Novaky
IS31
IS26
SEL3 event built with 3 Infra+1 Seismic arrays
Automatic location 75km from Ground Truth
CTBTO/IDC
4 km
Event location refined by analysts
REB Location is 5km from GT
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processing
Atmospheric modeling: Case study (IRED)
Novaky explosion, Waveforms and DFX-PMCC detections
I26DE (350 km)
CTBTO/IDC
I31KZ (2825 km)
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
I46RU (4500 km)
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Enhancement of the automatic infra processing
Atmospheric modeling: Case study (IRED)
Novaky explosion, WASP-3D ray tracing at I26DE using different atm. models
Ray tracing (color=shooting angle)
100km
I26DE
Travel time curves
(color=Trace velocity)
I26DE
HWM93
100km
HWM07
100km
G2SECMWF
CTBTO/IDC
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processing
Atmospheric modeling: Case study (IRED)
Novaky explosion, WASP-3D ray tracing at I31KZ using different atm. models
Only stratospheric rays are displayed
Is branches
I31KZ
It branches
HWM93
50km
HWM07
50km
G2SECMWF
50km
I31KZ
CTBTO/IDC
Infrasound Technology Workshop in Bermuda, 3-7 November 2008
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Enhancement of the automatic infra processing
Atmospheric modeling: Case study (IRED)
Novaky explosion, Summary of ray tracing results (observed/predicted celerity and back az.
deviation)
I26DE
I31KZ
I46RU
DFX-PMCC
Cel.
(m/s)
256
307
305
∆Az
(deg.)
0.54
0.91
1.85
Atm. models
Taupc
WASP-3D
Sph
CTBTO/IDC
HWM93
G2SECMWF
HWM07
HWM93
G2SECMWF
HWM07
HWM93
G2SECMWF
Cel.
(m/s)
234
303
309
∆Az
(deg.)
0.85
-0.6
-1.0
HWM07
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
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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 processing
New 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)
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