1. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 1 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

2. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 2 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)

3. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 3 Preparing the Return of Infrasound in IDC Operations

4. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 4 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

5. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 5 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

6. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 6 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

7. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 7 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 1.5km 80m Robinson Crusoe I14CL 130m 110m 80m Inner sub-array at I14CL

8. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 8 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. Inner sub-array at I14CL 200m 180m 160m

9. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 9 Preparing the Return of Infrasound in IDC Ops Tuning of the Automatic Processing Before tuning 131 detections related to surf and microbaroms After tuning 74 detections related to surf and 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

10. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 10 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 All SHI events SHI events using new criteria Review signal detections & events Geotool-PMCC IRED Database InfraNet

11. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 11 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

12. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 12 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: - 179 SEL3 events (SHI) - 45 “infra” events before GA criteria - 17 “infra” events after GA criteria (min. 5, max. 32) Before criteriaAfter criteria

13. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 13 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 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 Database problem

14. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 14 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

15. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 15 Enhancement of the automatic infrasound processing: Atmospheric modeling - Models and tools -

16. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 16 Enhancement of the automatic infra processing Atmospheric models available at the IDC Zonal winds at latitude 49N 2 March 2007 @15:00 GMT G2S-ECMWF HWM93 = 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 Altitude (km) Longitude

17. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 17 Enhancement of the automatic infra processing Atmospheric models available at the IDC G2S-ECMWF HWM93 HWM07 Meridional winds at latitude 49N 2 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 Altitude (km) Longitude

18. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 18 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) Distance (km) Traveltimes (s) 200 800 1400 240300 360 I26DE 0 SourceI26DE Altitude (km) 150 75 0.46 V T (km/s) 0.36 * Windy Atmospheric Sonic Propagation 3D in Spherical Coordinates

19. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 19 Novaky explosion (Slovakia), 2 March 2007 @ 15:28:04 GMT Enhancement of the automatic infra processing Atmospheric modeling: Case study (IRED) Slovakia Hungary Czech Rep. Poland Austria IS26 IS31 IS46 VRAC GERES 4500 km 2825 km IS46 IS3 1 Novaky Explosion 4 km REB Event location refined by analysts REB Location is 5km from GT SEL3 event built with 3 Infra+1 Seismic arrays Automatic location 75km from Ground Truth Source: EMSC and P.Labak

20. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 20 Enhancement of the automatic infra processing Atmospheric modeling: Case study (IRED) I26DE (350 km) I31KZ (2825 km) I46RU (4500 km) Novaky explosion, Waveforms and DFX-PMCC detections

21. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 21 Enhancement of the automatic infra processing Atmospheric modeling: Case study (IRED) Novaky explosion, WASP-3D ray tracing at I26DE using different atm. models HWM93 HWM07 G2S- ECMWF I26DE Ray tracing (color=shooting angle) Travel time curves (color=Trace velocity) I26DE 100km

22. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 22 Enhancement of the automatic infra processing Atmospheric 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 50km

23. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 23 I26DEI31KZI46RU DFX-PMCC Cel. (m/s) 256307305 ∆Az (deg.) 0.540.911.85 Atm. models HWM93 G2S- ECMWF HWM07HWM93 G2S- ECMWF HWM07HWM93 G2S- ECMWF HWM07 Taupc Cel. (m/s) 234303309 ∆Az (deg.) 0.85-0.6 WASP-3D Sph Cel. (m/s) 235238235304-312303-308299-304295-300300-304295-301 ∆Az (deg.) 1.21.11.01.55-1.80.95-1.350.7-1.43.5-4.03.0-3.21.75-2.1 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)

24. CTBTO/IDC Infrasound Technology Workshop in Bermuda, 3-7 November 2008 24 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)