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Processing of the new Infrasound Arrays on the IDC Testbed - Initial Experience

Processing of the new Infrasound Arrays on the IDC Testbed - Initial Experience. Nicolas Brachet Acoustic officer, CTBTO/IDC/SM Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization Provisional Technical Secretariat Vienna International Centre P.O.Box 1200

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Processing of the new Infrasound Arrays on the IDC Testbed - Initial Experience

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  1. Processing of the new Infrasound Arrays on the IDC Testbed - Initial Experience • Nicolas Brachet • Acoustic officer, CTBTO/IDC/SM • Preparatory Commission for the • Comprehensive Nuclear-Test-Ban Treaty Organization • Provisional Technical Secretariat • Vienna International Centre • P.O.Box 1200 • A-1400 Vienna • AUSTRIA • Nicolas.Brachet@ctbto.org • Presented at the Infrasound workshop in Kona, Hawaii • November 2001

  2. Outline of the talk • Data received and processed at the IDC • Infrasound processing at the IDC • Goals and motivations for improvement of the system • Case studies • Problems in the processing of infrasound data at the IDC

  3. Incorporation of new IMS stations in IDC processing • IDC is using two processing pipelines in parallel • Operations: automatic and interactive analysis performed on a daily basis - generates the IDC products for distribution • Testbed: mirror of Operations used as a testing environment (software development, software configuration, integration of new stations in the processing) • In 2001, IDC is processing the data from 6 IMS infra stations • IS07 (Australia): September 2001 (Testbed), October 2001 (Operations) • IS08 (Bolivia): August 2001 (Testbed), November 2001 (approved for ops) • IS10 (Canada): September 2001 (Testbed), October 2001 (Operations) • IS26 (Germany): April 2001 (Testbed), October 2001 (Operations) • IS34 (Mongolia): August 2001 (Testbed) • IS57 (USA): October 2001 (Testbed)

  4. Goals and motivations • Improvement of the know-how in infrasound processing • Need for a better understanding of the signals Establishment of a catalog of reference events A few case studies presented in this talk • Becoming familiar with the latest methods in infrasound processing Assessment of existing tools used at the IDC New developments in infrasound signal processing (in 2001, cooperation with French NDC: PMCC is being tested at the IDC) • Station tuning • Currently at the IDC: standard configuration used for all stations • Need to include station specifics in the processing Assessment of the detection capability for each station

  5. Reference events collected in 2001 at the IDC • Pacific bolide (23 Apr 2001) • Earthquakes in Peru (23 Jun, 26 Jun, 7 Jul 2001) • Eruption of the Etna volcano, Italy (Jul 2001) • Explosion at a chemical factory in Toulouse, France (20 Sep 2001) • Mining activity in Canada (11 Sep 2001)

  6. Case study: Pacific bolide (23-Apr-2001) Validation of PMCC results on a well-studied event

  7. PERU Titicaca lake IS08 Ms=8.2 Ms=6.9 Ms=7.5 Ms=6.8 23-Jun-2001 BOLIVIA 26-Jun-2001 07-Jul-2001 100 km Topography data: USGS DEM & Cornell Andes Project Case study: seismic event in Peru (Jun-Jul 2001) Event detected at a distance of 500km at IS08 (Bolivia)

  8. seismic seismic 1 5 4 3 2 6 Case study: seismic event in Peru - 23 Jun 2001 Results of PMCC analysis

  9. Case study: seismic event in Peru - 23 Jun 2001 (Cont.) • REB events in Peru detected by PMCC at IS08 • Most seismic events with mb>5 detected at IS08 • Phases detected: Seismic waves (P and Rayleigh) for large events • Many infrasound phases arrive earlier than expected (I*)

  10. Case study: seismic event in Peru - 07 Jul 2001 Comparison of results for REB event in Peru (07 Jul 2001) • PMCC produced the same type of results as for June 23 event • Libinfra-PIDC detected only the seismic arrivals • Note: phases identified as Noise by StaPro (cannot be associated to an automatic event)

  11. Case study: seismic event in Peru - 07 Jul 2001 (Cont.) Azimuth variation reflects the geomorphology of the Andes Polar diagram of the infra arrivals 3 1 1’ 2 3 1 1’ 2 infra seismic IS08 3 1 REB Event 1’ Ms=7.5 2 The Andean cordillera behaves like multiple infrasound sources activated by the seismic wave front

  12. Infra-Seismic stations co-located in Canada Mining activities recorded at the Canadian stations: IS10 + ULM Lake Winnipeg 200km ULM IS10 Lake Superior 400km

  13. PMCC analysis at IS10 (Canada)

  14. Identification of the events recorded at IS10 Categorization of station-specific events LOCAL MINES MESABI RANGE (400km SE) 200km NE

  15. Infrasound and meteorology: microbaroms at IS26 (Germany) • Detections with similar characteristics over a long time period • Detections produced by DFX-Libinfra, confirmed by PMCC • No correlation with any microbaroms at Flers (France) • Meteorology data: storm in the North Sea the same day

  16. Problems with data processing at the IDC • Low and irregular number of detections observed for all infrasound stations processed at the IDC • Possible cause of the problems • Software related: algorithm, configuration • Data related • Case of IS26 (Germany)

  17. Problems with data processing at the IDC(Cont.) • Asynchronous Testbed and Operations pipelines • Data is forwarded from ops to Testbed in near real time • Data is organized in time intervals of 30min for infra • Intervals are scheduled for processing when they contain a sufficient amount of data • Problem 1: Intervals are processed in near real time: all data needed may not be available for use at the time it is processed • Problem 2: Interval generation and execution is asynchronously done on ops and Testbed • Consequences for the detection process: • Ops and Testbed may process different data • Ops and Testbed may produce different detections

  18. Testbed : I26DE (processing time interval [16:00 - 16:30] on October 16, 2001) ++ tuxshell 2001-10-16 16:34:10 time=1003248000.000 endtime=1003249800.000 name=I26DE get_infra_processing_interval: Requested processing interval 1003248000.000 to 1003249800.000 get_infra_processing_interval: Computed processing interval 1003247999.983 to 1003249632.033 get_infra_processing_interval: Actual waveform data interval 1003247860.885 to 1003249839.957 -- tuxshell 2001-10-16 16:35:01 time=1003248000.000 endtime=1003249800.000 name=I26DE Operations : I26DE (processing time interval [16:00 - 16:30] on October 16, 2001) ++ tuxshell 2001-10-16 16:34:26 time=1003248000.000 endtime=1003249800.000 name=I26DE get_infra_processing_interval: Requested processing interval 1003248000.000 to 1003249800.000 get_infra_processing_interval: Computed processing interval 1003247999.983 to 1003249712.033 get_infra_processing_interval: Actual waveform data interval 1003247860.885 to 1003249919.957 -- tuxshell 2001-10-16 16:35:20 time=1003248000.000 endtime=1003249800.000 name=I26DE Problems with data processing at the IDC - Example

  19. All channel subframes of a Data Frame will have the same start time and duration to within one sample time unit. […] The nominal time field is set equal to the start time of the earliest channel subframe [...] on an interval multiple of 10 seconds and synchronized to the minute(Format and Protocol for Cont. data CD-1.1). Nominal timestamp of the data frame 1 sample (0.05s) 20 seconds Channel subframe Start_time of subframe 20s shift in wfdisc segments Irregular Data frames (within 1 sample) Problems with data processing at the IDC (Cont.) • Digitizing problems at IS26 causes asynchronous wfdiscs

  20. Problems with data processing at the IDC (Cont.) • The number of detections is lower when Wfdisc segments are asynchronous 4 chans 5 chans Number of synchronous channels: 3 chans 12345 12345 12345 12345 12345 12345

  21. Problems with data processing at the IDC (Cont.) Spectral analysis at IS26 • Presence of multiple peaks on all channels • origins of the peaks? • impact on the processing?

  22. Summary • Infrasound signal analysis is a difficult exercise: collection of reference events is necessary • To increase the experience and knowledge in signal processing and event recognition • Familiarization with the detection capability of IMS stations • First step before starting a comprehensive station tuning • Assessment of the analysis tools: • Existing automatic system (detection/association) • PMCC interactive tool for signal analysis • Problem of low number of detections produced at the IDC • Related to the software • Related to the configuration parameters (tuning) • Related to the data

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