Infrasound Workshop San Diego, USA 27-30 October 2003

1. Infrasound WorkshopSan Diego, USA27-30 October 2003 Infrasound Processing at the IDC using DFX-PMCC N. Brachet International Data Centre Waveform Development Unit Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization Provisional Technical Secretariat Vienna International Centre P.O. Box 1200, A-1400 Vienna, Austria E-mail: Nicolas.Brachet@ctbto.org

2. Outline of the Talk • Software design and signal review • Started with the increased amount of infrasound data (# IMS stations processed at the IDC) • Understand the signal characteristics with the up-to-date interactive WinPMCC (DASE) • Software development • Upgrade the existing DFX-PMCC (as delivered in IDC Release 1) using WinPMCC as a reference • Establish a baseline configuration • Identify key parameters that impact on the DFX-PMCC detection capability • Propose generic DFX-PMCC parameters for processing IMS arrays • Software testing and validation • Reprocess the known infrasound events archived in the IDC reference database • Large scale testing in a real-time environment Infrasound Workshop in San Diego, USA

3. Milestones of DFX-PMCC at the IDC • A few dates: • June 1998: Installation of DFX-PMCC at the PIDC, Arlington • April 2001: First IMS station (I26DE) processed at the IDC • July 2001: Delivery of WinPMCC V1.0.4 • June 2002: DFX-PMCC run offline, results monitored on IDC infrasound intranet • Summer 2002: IDC analysts test WinPMCC - Validation of the method • February 2002: Plans for design of future infrasound processing at the IDC • 2003: DFX-PMCC/WinPMCC comparison - Bug corrections • Major update of DFX-PMCC source code (3D results) • September 2003: Baseline configuration of DFX-PMCC - validation on reference events • November 2003 (Plan): DFX-PMCC on development LAN (real-time testing) Infrasound Workshop in San Diego, USA

4. DFX-PMCC Software Development • Major modifications of the structure of the software • Produce and store 3D pixels containing the derived data (az,sp,f,t) into files • Store the results into IDC database using • The usual DFX tables: ARRIVAL, DETECTION, WFDISC • additional tables: PMCC_FEATURES, DERVDISC, PMCC_RECIPE • Enhancements and corrections of existing modules • Improve the azimuth calculation for PMCC families • Use relative speed instead of absolute speed when grouping the pixels (detection of seismic phases) • handle dead channels or met. data in the processing • Improve the module in charge of closing/merging large families • Increase the maintainability: Clean unused source code (10% of total) and comment source code Infrasound Workshop in San Diego, USA

5. DFX-PMCC Software Development • Synchronize DFX-PMCC and WinPMCC results • Bring DFX-PMCC at the same level of confidence as WinPMCC (the reference) Long March rocket launch detected at I34MN, 15 Oct 2003 Azimuth Speed DFX-PMCC WinPMCC Infrasound Workshop in San Diego, USA

6. Air France British Airways Baseline Configuration for DFX-PMCC • Key factors impacting on DFX-PMCC detection capability • Preprocessing: DFX Data Quality Control (QC) • Frequency resolution: Selection of frequency bands and filters • Azimuth resolution • Selection of the best sub-network combination • Control the number of events per station: “size” of signals to be detected • Accomplishments DFX-PMCC in Jan2003 Baseline config. DFX-PMCC in Sep2003 Infrasound Workshop in San Diego, USA

7. Baseline Configuration for DFX-PMCC DFX-Quality Control (QC) Objective: Remove the HF bogus detections • Action: Reduce DFX-QC action • DFX-QC generates unstable bogus PMCC detections at high frequency • DFX-QC searches and masks poor quality samples - Waveforms are repaired (interpolation) when possible • Two levels of Data QC: basic (spikes, gaps, sequences) and extended (complex spikes, multi-channel analysis) • Turn off the extended QC and use only a basic QC for gaps, sequences and larger spikes • Results:Close to 100% of bogus HF detections have disappeared Infrasound Workshop in San Diego, USA

8. Baseline Configuration for DFX-PMCC DFX-Quality Control • Objective: Reduce the sensitivity of DFX-PMCC to microbaroms • Preliminary observation: understand the signal characteristics • Microbaroms produced by marine storms • Narrow band signals ~0.1 - 0.4 Hz • Series of signal bursts that can be detected over long time periods (typically several hours) • More variation in detection azimuths when the source is closer to the station Infrasound Workshop in San Diego, USA

9. PMCC Pixel (az,sp,f,t) PMCC Family avg(az,sp,f,t) Frequency band Frequency band [0.1-0.4] time time Microbaroms detection Baseline Configuration for DFX-PMCC Frequency Bands • Action: Use lower weight in the processing of specific freq. bands • Do not use a band-stop filters • Take advantage of the PMCC method for clustering pixels into detection families • Detection pixels are those which verify the consistency relation • Pixels with similar attributes (az,sp,f,t) are grouped into families • Families are turned into detections if they contain a minimum number of pixels Infrasound Workshop in San Diego, USA

10. Baseline Configuration for DFX-PMCC Frequency Bands I26DE, 12 Jan 2003 Isolated pixels with different characteristics -> No detection Pixels, az [0.1-0.4] Families, az Isolated pixels with similar characteristics (microbaroms) -> No detection Pixels, sp Families, sp 3 families of pixels = 3 detections • Results: • “Trap” the microbaroms detections in a narrow frequency band. • Post-processing can be applied in order to identify these detections and not to use them in subsequent stages of processing (event building) • Remove the smallest sequences of microbaroms • Same logic can be applied to any narrow band signal Infrasound Workshop in San Diego, USA

11. Chebychev [0.1-0.3], order 2 Chebychev [0.1-0.3], order 3 Baseline Configuration for DFX-PMCC Frequency Resolution • Objective:Improve the frequency resolution of the signal detected • Signals like microbaroms are detected by DFX-PMCC at frequencies up to 1Hz • Action: Use a band-pass filter that has a steep roll off • Results: • Slightly decreases the detection capability but substantially improves the frequency resolution • The microbaroms detected by DFX-PMCC are more constrained to lower frequencies <0.5Hz Infrasound Workshop in San Diego, USA

12. Source: FNMOC Wave Watch 3 (WW3) Baseline Configuration for DFX-PMCC Frequency Resolution Examples of microbaroms detected at I07AU (6 Sep2003) DFX-PMCC, Chebychev order 2 I07AU DFX-PMCC, Chebychev order 3 (Steeper roll-off) Infrasound Workshop in San Diego, USA

13. Baseline Configuration for DFX-PMCC Azimuth Resolution • Objective: Improve the azimuth resolution • Trigger detections on signals with stable characteristics, focus on azimuth stability • Prepare for a basic event categorization • Action: • Use a low threshold in azimuth when forming the PMCC families (+/- 6 or 10 degrees) • Find a good compromise between a good azimuth resolution and high number of detections produced (split families). Risk of merging independent families if the azimuth criterion is too loose. Unstable detections Azimuth threshold “Event” categorization Split families (Total # of detections) Azimuth accuracy Missed small detections Infrasound Workshop in San Diego, USA

14. Baseline Configuration for DFX-PMCC Azimuth Resolution Results: Example of microbaroms at I07AU (6 Sep 2003) • Parameter: • Daz = +/- 10 deg • Output: • 55 detections • backaz = 225.5 +/- 7.7 • Parameter: • Daz = +/- 6 deg • Output: • 89 detections • backaz = 224.7 +/- 5.4 Infrasound Workshop in San Diego, USA

15. Baseline Configuration for DFX-PMCC Array Geometry • Objective: • Study how the selection of array geometry impacts on the detection capability • Results presented at the IMS infrasound meeting in Vienna, March 2003 • Action: • For identified signals (Concorde, microbaroms) check the detections when removing one array element from the processing • Results: • Good detection capability and quality of PMCC even with low number of array elements (4) • Good detection capability of small aperture arrays well complemented by quality of detection features provided by large aperture arrays • The central element plays a key role in the PMCC detection processing • DFX-PMCC shall configuration includes a large number of combinations of sub-networks • Plan: intelligent selection of sub-networks based on data channel QC (Future evolution) Infrasound Workshop in San Diego, USA

16. Az 320 Az 80 Az Sp All Az Sp -H1 Az Sp -H2 Az Sp -H3 Az Baseline Configuration for DFX-PMCC Array Geometry Sp -H4 I34H1 Az 80 Example: I34MN 18 Jan 2003 microbaroms between 8:00-12:00 GMT Infrasound Workshop in San Diego, USA

17. PMCC Pixel (az,sp,f,t) PMCC Family avg(az,sp,f,t) Frequency band Frequency band time time Baseline Configuration for DFX-PMCC Detection Threshold • Objective: Set the minimum “size of events” to be detected • DFX-PMCC does not work with amplitudes (no minimum SNR threshold applied) • The “size” of the signal to be detected depends on the minimum number of pixels per family • It is the last parameter to be tuned according to the types of events detected at the station Family would not be built if min. number of pixels<5 Infrasound Workshop in San Diego, USA

18. Baseline Configuration for DFX-PMCC Detection Threshold • Example: Argyle mine at I07AU, ML2.4 730km (16Apr2002) Pixel threshold=15 -> 13 detections Pixel threshold=100 -> 1 detection Pixels Pixels Families Families SNR=9.8 Infrasound Workshop in San Diego, USA

19. a Good quality detection a Poor quality detection r No detection x Not available DFX-PMCC testing and validation Test the baseline configuration of DFX-PMCC on the 30 IDC infra. ref. events 2001SEL3DFX-PMCC Day Event description IMS array Seismic Infra Seismic Infra 23 Apr North Pacific bolide I10CA x x I26DE x x I59US xa 23 Jun Peru main earthquake I08BO x x a a 23 Jun Peru aftershock I08BO x x ra 7 Jul Peru earthquake I08BO x x x x 15 July Etna eruption I26DE r x 21 Sep Toulouse explosion I26DE a a 14 Oct Canada bolide I10CA (!) rx 21 Oct Nuremberg explosion I26DE ra 14 Nov China earthquake I34MN a a a a 18 Nov Leonid meteorite I59US xa 2002 26 Jan US missile test I59US ra 9 Mar Central Pacific bolide I10CA (!) aa I57US x a I59US aa 12 Mar Space Shuttle STS109 I10CA (!) ra 6 Apr Germany bolide I26DE aa Infrasound Workshop in San Diego, USA

20. a Good quality detection a Poor quality detection r No detection x Not available DFX-PMCC testing and validation Test the baseline configuration of DFX-PMCC on the 30 IDC infra. ref. events 2002 (Cont.)SEL3DFX-PMCC Day Event description IMS array Seismic Infra Seismic Infra 16 Apr Argyle mine I07AU aa 6 Jun Mediterranean sea bolide I26DE aa 8 Sep New Guinea earthquake I07AU ar 28 Sep Watusi explosion I10CA (cor.) ra 28 Sep Indonesia earthquake I07AU aaaa 23 Oct Alaska earthquake I10CA (cor.) xa x a 3 Nov Alaska earthquake I10CA (cor.) aaaa 2003 1 Feb Space Shuttle STS107 I10CA (cor.) aa 1 Feb Concorde I26DE ra 27 Mar Explosion Billy-Berclau I26DE ra 8 Jun Soyuz rocket launch I31KZ aa 12 Aug Soyuz rocket launch I31KZ aa 14 Aug Greece earthquake I26DE ra 27 Aug Hawaii earthquake I59US aa 29 Aug Soyuz rocket launch I31KZ aa 15 Oct LongMarch rocket launch I34MN aa Infrasound Workshop in San Diego, USA

21. Summary • History of DFX-PMCC connected to • The amount of infrasound data processed at the IDC (# of IMS stations) • Large contribution of WinPMCC (new vision for presenting the derived results) • DFX-PMCC provides a powerful automatic detector for infrasound signals with • Good detection capability and feature extraction quality • Large variety of signals detected • Low level of false alarms • DFX-PMCC brings reliability into IDC infrasound processing • Since September 2003, Maturity of the software and high level of confidence • The baseline configuration has been successfully tested on the IDC reference events • Plans for the near future • Large scale testing in a real-time environment is to be initiated (November 2003) • Limit the impact of long duration signals on the automatic processing • Develop in parallel the future interactive infrasound software at the IDC Infrasound Workshop in San Diego, USA