1. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 6 Case study: Pacific bolide (23-Apr-2001) Validation of PMCC results on a well-studied event

7. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 7 Case study: seismic event in Peru (Jun-Jul 2001) IS08 Titicaca lake Ms=8.2 Ms=6.8 BOLIVIA PERU Topography data: USGS DEM & Cornell Andes Project 100 km 23-Jun-2001 26-Jun-2001 07-Jul-2001 Ms=6.9 Ms=7.5 Event detected at a distance of 500km at IS08 (Bolivia)

8. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 8 Case study: seismic event in Peru - 23 Jun 2001 seismic 1 2 4 6 3 5 Results of PMCC analysis

9. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 9 Case study: seismic event in Peru - 23 Jun 2001 (Cont.) 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*) REB events in Peru detected by PMCC at IS08

10. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 10 Case study: seismic 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 Comparison of results for REB event in Peru (07 Jul 2001) Note: phases identified as Noise by StaPro (cannot be associated to an automatic event)

11. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 11 Case study: seismic event in Peru - 07 Jul 2001 (Cont.) 1 2 3 3 2 Polar diagram of the infra arrivals seismic infra 1 2 1 3 1 1 1 Ms=7.5 IS08 REB Event The Andean cordillera behaves like multiple infrasound sources activated by the seismic wave front Azimuth variation reflects the geomorphology of the Andes

12. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 12 Infra-Seismic stations co-located in Canada Mining activities recorded at the Canadian stations: IS10 + ULM Lake Winnipeg Lake Superior IS10 200km 400km ULM

13. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 13 PMCC analysis at IS10 (Canada)

14. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 14 Identification of the events recorded at IS10 MESABI RANGE (400km SE) LOCAL MINES Categorization of station-specific events 200km NE

15. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 16 Possible cause of the problems Software related: algorithm, configuration Data related Case of IS26 (Germany) Problems with data processing at the IDC Low and irregular number of detections observed for all infrasound stations processed at the IDC

17. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 18 Problems with data processing at the IDC - Example 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

19. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 19 Problems with data processing at the IDC (Cont.) Nominal timestamp of the data frame Start_time of subframe Irregular Data frames (within 1 sample) 20s shift in wfdisc segments 1 sample (0.05s) Channel subframe 20 seconds 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). Digitizing problems at IS26 causes asynchronous wfdiscs

20. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 20 Problems with data processing at the IDC (Cont.) 12345 5 chans 4 chans 3 chans Number of synchronous channels: The number of detections is lower when Wfdisc segments are asynchronous

21. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 21 Problems with data processing at the IDC (Cont.) Presence of multiple peaks on all channels origins of the peaks? impact on the processing? Spectral analysis at IS26

22. International Data Centre Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization 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