ctbto/idc infrasound technology workshop in bermuda, 3-7 november 2008 1 preparing the return of...

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


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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)


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Preparing the Return ofInfrasound in IDC Operations


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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Enhancement of the automatic infrasound processing:

Atmospheric modeling

- Models and tools -


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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


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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


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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


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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


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I26DE (350 km) I31KZ (2825 km) I46RU (4500 km)

Novaky explosion, Waveforms and DFX-PMCC detections


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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


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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


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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


Novaky explosion, Summary of ray tracing results (observed/predicted celerity and back az. deviation)


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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)

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