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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
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
outline of the talk
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
incorporation of new ims stations in idc processing
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)
goals and motivations
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

reference events collected in 2001 at the idc
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)
case study pacific bolide 23 apr 2001
Case study: Pacific bolide (23-Apr-2001)

Validation of PMCC results on a well-studied event

case study seismic event in peru jun jul 2001

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)

case study seismic event in peru 23 jun 2001

seismic

seismic

1

5

4

3

2

6

Case study: seismic event in Peru - 23 Jun 2001

Results of PMCC analysis

case study seismic event in peru 23 jun 2001 cont
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*)
case study seismic event in peru 07 jul 2001
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)
case study seismic event in peru 07 jul 2001 cont
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

infra seismic stations co located in canada
Infra-Seismic stations co-located in Canada

Mining activities recorded at the Canadian stations: IS10 + ULM

Lake Winnipeg

200km

ULM

IS10

Lake Superior

400km

identification of the events recorded at is10
Identification of the events recorded at IS10

Categorization of station-specific events

LOCAL MINES

MESABI RANGE (400km SE)

200km NE

infrasound and meteorology microbaroms at is26 germany
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
problems with data processing at the idc
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)
problems with data processing at the idc cont
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
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

Problems with data processing at the IDC - Example
problems with data processing at the idc cont1

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
problems with data processing at the idc cont2
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

problems with data processing at the idc cont3
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?
summary
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